🏗 Merge C++ into python codebase (#504)

## Description:

Move esphome-core codebase into esphome (and a bunch of other refactors). See https://github.com/esphome/feature-requests/issues/97

Yes this is a shit ton of work and no there's no way to automate it :( But it will be worth it 👍

Progress:
- Core support (file copy etc): 80%
- Base Abstractions (light, switch): ~50%
- Integrations: ~10%
- Working? Yes, (but only with ported components).

Other refactors:
- Moves all codegen related stuff into a single class: `esphome.codegen` (imported as `cg`)
- Rework coroutine syntax
- Move from `component/platform.py` to `domain/component.py` structure as with HA
- Move all defaults out of C++ and into config validation.
- Remove `make_...` helpers from Application class. Reason: Merge conflicts with every single new integration.
- Pointer Variables are stored globally instead of locally in setup(). Reason: stack size limit.

Future work:
- Rework const.py - Move all `CONF_...` into a conf class (usage `conf.UPDATE_INTERVAL` vs `CONF_UPDATE_INTERVAL`). Reason: Less convoluted import block
- Enable loading from `custom_components` folder.

**Related issue (if applicable):** https://github.com/esphome/feature-requests/issues/97

**Pull request in [esphome-docs](https://github.com/esphome/esphome-docs) with documentation (if applicable):** esphome/esphome-docs#<esphome-docs PR number goes here>

## Checklist:
  - [ ] The code change is tested and works locally.
  - [ ] Tests have been added to verify that the new code works (under `tests/` folder).

If user exposed functionality or configuration variables are added/changed:
  - [ ] Documentation added/updated in [esphomedocs](https://github.com/OttoWinter/esphomedocs).

esphome/components/rdm6300/__init__.py

@@ -0,0 +1,30 @@
+import esphome.codegen as cg
+import esphome.config_validation as cv
+from esphome import automation
+from esphome.components import uart
+from esphome.const import CONF_ID, CONF_ON_TAG, CONF_TRIGGER_ID
+
+DEPENDENCIES = ['uart']
+AUTO_LOAD = ['binary_sensor']
+
+rdm6300_ns = cg.esphome_ns.namespace('rdm6300')
+RDM6300Component = rdm6300_ns.class_('RDM6300Component', cg.Component, uart.UARTDevice)
+RDM6300Trigger = rdm6300_ns.class_('RDM6300Trigger', cg.Trigger.template(cg.uint32))
+
+CONFIG_SCHEMA = cv.Schema({
+    cv.GenerateID(): cv.declare_variable_id(RDM6300Component),
+    cv.Optional(CONF_ON_TAG): automation.validate_automation({
+        cv.GenerateID(CONF_TRIGGER_ID): cv.declare_variable_id(RDM6300Trigger),
+    }),
+}).extend(cv.COMPONENT_SCHEMA).extend(uart.UART_DEVICE_SCHEMA)
+
+
+def to_code(config):
+    var = cg.new_Pvariable(config[CONF_ID])
+    yield cg.register_component(var, config)
+    yield uart.register_uart_device(var, config)
+
+    for conf in config.get(CONF_ON_TAG, []):
+        trigger = cg.new_Pvariable(conf[CONF_TRIGGER_ID])
+        cg.add(var.register_trigger(trigger))
+        yield automation.build_automation(trigger, [(cg.uint32, 'x')], conf)

esphome/components/rdm6300/binary_sensor.py

@@ -0,0 +1,23 @@
+import esphome.codegen as cg
+import esphome.config_validation as cv
+from esphome.components import binary_sensor, rdm6300
+from esphome.const import CONF_UID, CONF_ID, CONF_NAME
+from . import rdm6300_ns
+
+DEPENDENCIES = ['rdm6300']
+
+CONF_RDM6300_ID = 'rdm6300_id'
+RDM6300BinarySensor = rdm6300_ns.class_('RDM6300BinarySensor', binary_sensor.BinarySensor)
+
+CONFIG_SCHEMA = cv.nameable(binary_sensor.BINARY_SENSOR_SCHEMA.extend({
+    cv.GenerateID(): cv.declare_variable_id(RDM6300BinarySensor),
+    cv.GenerateID(CONF_RDM6300_ID): cv.use_variable_id(rdm6300.RDM6300Component),
+    cv.Required(CONF_UID): cv.uint32_t,
+}))
+
+
+def to_code(config):
+    hub = yield cg.get_variable(config[CONF_RDM6300_ID])
+    var = cg.new_Pvariable(config[CONF_ID], config[CONF_NAME], config[CONF_UID])
+    yield binary_sensor.register_binary_sensor(var, config)
+    cg.add(hub.register_card(var))

esphome/components/rdm6300/rdm6300.cpp

@@ -0,0 +1,69 @@
+#include "rdm6300.h"
+#include "esphome/core/log.h"
+
+namespace esphome {
+namespace rdm6300 {
+
+static const char *TAG = "rdm6300";
+
+static const uint8_t RDM6300_START_BYTE = 0x02;
+static const uint8_t RDM6300_END_BYTE = 0x03;
+static const int8_t RDM6300_STATE_WAITING_FOR_START = -1;
+
+void rdm6300::RDM6300Component::loop() {
+  while (this->available() > 0) {
+    uint8_t data;
+    if (!this->read_byte(&data)) {
+      ESP_LOGW(TAG, "Reading data from RDM6300 failed!");
+      this->status_set_warning();
+      return;
+    }
+
+    if (this->read_state_ == RDM6300_STATE_WAITING_FOR_START) {
+      if (data == RDM6300_START_BYTE) {
+        this->read_state_ = 0;
+      } else {
+        // Not start byte, probably not synced up correctly.
+      }
+    } else if (this->read_state_ < 12) {
+      uint8_t value = (data > '9') ? data - '7' : data - '0';
+      if (this->read_state_ % 2 == 0) {
+        this->buffer_[this->read_state_ / 2] = value << 4;
+      } else {
+        this->buffer_[this->read_state_ / 2] += value;
+      }
+      this->read_state_++;
+    } else if (data != RDM6300_END_BYTE) {
+      ESP_LOGW(TAG, "Invalid end byte from RDM6300!");
+      this->read_state_ = RDM6300_STATE_WAITING_FOR_START;
+    } else {
+      uint8_t checksum = 0;
+      for (uint8_t i = 0; i < 5; i++)
+        checksum ^= this->buffer_[i];
+      this->read_state_ = RDM6300_STATE_WAITING_FOR_START;
+      if (checksum != this->buffer_[5]) {
+        ESP_LOGW(TAG, "Checksum from RDM6300 doesn't match! (0x%02X!=0x%02X)", checksum, this->buffer_[5]);
+      } else {
+        // Valid data
+        this->status_clear_warning();
+        const uint32_t result = (uint32_t(this->buffer_[1]) << 24) | (uint32_t(this->buffer_[2]) << 16) |
+                                (uint32_t(this->buffer_[3]) << 8) | this->buffer_[4];
+        bool report = result != last_id_;
+        for (auto *card : this->cards_) {
+          if (card->process(result)) {
+            report = false;
+          }
+        }
+        for (auto *trig : this->triggers_)
+          trig->process(result);
+
+        if (report) {
+          ESP_LOGD(TAG, "Found new tag with ID %u", result);
+        }
+      }
+    }
+  }
+}
+
+}  // namespace rdm6300
+}  // namespace esphome

esphome/components/rdm6300/rdm6300.h

@@ -0,0 +1,55 @@
+#pragma once
+
+#include "esphome/core/component.h"
+#include "esphome/core/automation.h"
+#include "esphome/components/binary_sensor/binary_sensor.h"
+#include "esphome/components/uart/uart.h"
+
+namespace esphome {
+namespace rdm6300 {
+
+class RDM6300BinarySensor;
+class RDM6300Trigger;
+
+class RDM6300Component : public Component, public uart::UARTDevice {
+ public:
+  void loop() override;
+
+  void register_card(RDM6300BinarySensor *obj) { this->cards_.push_back(obj); }
+  void register_trigger(RDM6300Trigger *trig) { this->triggers_.push_back(trig); }
+
+  float get_setup_priority() const override { return setup_priority::DATA; }
+
+ protected:
+  int8_t read_state_{-1};
+  uint8_t buffer_[6]{};
+  std::vector<RDM6300BinarySensor *> cards_;
+  std::vector<RDM6300Trigger *> triggers_;
+  uint32_t last_id_{0};
+};
+
+class RDM6300BinarySensor : public binary_sensor::BinarySensor {
+ public:
+  RDM6300BinarySensor(const std::string &name, uint32_t id) : BinarySensor(name), id_(id) {}
+
+  bool process(uint32_t id) {
+    if (this->id_ == id) {
+      this->publish_state(true);
+      yield();
+      this->publish_state(false);
+      return true;
+    }
+    return false;
+  }
+
+ protected:
+  uint32_t id_;
+};
+
+class RDM6300Trigger : public Trigger<uint32_t> {
+ public:
+  void process(uint32_t uid) { this->trigger(uid); }
+};
+
+}  // namespace rdm6300
+}  // namespace esphome