🏗 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/remote_receiver/remote_receiver_esp8266.cpp

@@ -0,0 +1,123 @@
+#include "remote_receiver.h"
+#include "esphome/core/log.h"
+#include "esphome/core/helpers.h"
+
+#ifdef ARDUINO_ARCH_ESP8266
+
+namespace esphome {
+namespace remote_receiver {
+
+static const char *TAG = "remote_receiver.esp8266";
+
+void ICACHE_RAM_ATTR HOT RemoteReceiverComponentStore::gpio_intr(RemoteReceiverComponentStore *arg) {
+  const uint32_t now = micros();
+  // If the lhs is 1 (rising edge) we should write to an uneven index and vice versa
+  const uint32_t next = (arg->buffer_write_at + 1) % arg->buffer_size;
+  if (uint32_t(arg->pin->digital_read()) != next % 2)
+    return;
+  const uint32_t last_change = arg->buffer[arg->buffer_write_at];
+  if (now - last_change <= arg->filter_us)
+    return;
+
+  arg->buffer[arg->buffer_write_at = next] = now;
+
+  if (next == arg->buffer_read_at) {
+    arg->overflow = true;
+  }
+}
+
+void RemoteReceiverComponent::setup() {
+  ESP_LOGCONFIG(TAG, "Setting up Remote Receiver...");
+  this->pin_->setup();
+  auto &s = this->store_;
+  s.filter_us = this->filter_us_;
+  s.pin = this->pin_->to_isr();
+  s.buffer_size = this->buffer_size_;
+
+  this->high_freq_.start();
+  if (s.buffer_size % 2 != 0) {
+    // Make sure divisible by two. This way, we know that every 0bxxx0 index is a space and every 0bxxx1 index is a mark
+    s.buffer_size++;
+  }
+  s.buffer = new uint32_t[s.buffer_size];
+  // First index is a space.
+  if (this->pin_->digital_read()) {
+    s.buffer_write_at = s.buffer_read_at = 1;
+    s.buffer[1] = 0;
+    s.buffer[0] = 0;
+  } else {
+    s.buffer_write_at = s.buffer_read_at = 0;
+    s.buffer[0] = 0;
+  }
+  this->pin_->attach_interrupt(RemoteReceiverComponentStore::gpio_intr, &this->store_, CHANGE);
+}
+void RemoteReceiverComponent::dump_config() {
+  ESP_LOGCONFIG(TAG, "Remote Receiver:");
+  LOG_PIN("  Pin: ", this->pin_);
+  if (this->pin_->digital_read()) {
+    ESP_LOGW(TAG, "Remote Receiver Signal starts with a HIGH value. Usually this means you have to "
+                  "invert the signal using 'inverted: True' in the pin schema!");
+  }
+  ESP_LOGCONFIG(TAG, "  Buffer Size: %u", this->buffer_size_);
+  ESP_LOGCONFIG(TAG, "  Tolerance: %u%%", this->tolerance_);
+  ESP_LOGCONFIG(TAG, "  Filter out pulses shorter than: %u us", this->filter_us_);
+  ESP_LOGCONFIG(TAG, "  Signal is done after %u us of no changes", this->idle_us_);
+}
+
+void RemoteReceiverComponent::loop() {
+  auto &s = this->store_;
+  if (s.overflow) {
+    s.buffer_read_at = s.buffer_write_at;
+    s.overflow = false;
+    ESP_LOGW(TAG, "Data is coming in too fast! Try increasing the buffer size.");
+    return;
+  }
+
+  // copy write at to local variables, as it's volatile
+  const uint32_t write_at = s.buffer_write_at;
+  const uint32_t dist = (s.buffer_size + write_at - s.buffer_read_at) % s.buffer_size;
+  // signals must at least one rising and one leading edge
+  if (dist <= 1)
+    return;
+  const uint32_t now = micros();
+  if (now - s.buffer[write_at] < this->idle_us_)
+    // The last change was fewer than the configured idle time ago.
+    // TODO: Handle case when loop() is not called quickly enough to catch idle
+    return;
+
+  ESP_LOGVV(TAG, "read_at=%u write_at=%u dist=%u now=%u end=%u", s.buffer_read_at, write_at, dist, now,
+            s.buffer[write_at]);
+
+  // Skip first value, it's from the previous idle level
+  s.buffer_read_at = (s.buffer_read_at + 1) % s.buffer_size;
+  uint32_t prev = s.buffer_read_at;
+  s.buffer_read_at = (s.buffer_read_at + 1) % s.buffer_size;
+  const uint32_t reserve_size = 1 + (s.buffer_size + write_at - s.buffer_read_at) % s.buffer_size;
+  this->temp_.clear();
+  this->temp_.reserve(reserve_size);
+  int32_t multiplier = s.buffer_read_at % 2 == 0 ? 1 : -1;
+
+  for (uint32_t i = 0; prev != write_at; i++) {
+    int32_t delta = s.buffer[s.buffer_read_at] - s.buffer[prev];
+    if (uint32_t(delta) >= this->idle_us_) {
+      // already found a space longer than idle. There must have been two pulses
+      break;
+    }
+
+    ESP_LOGVV(TAG, "  i=%u buffer[%u]=%u - buffer[%u]=%u -> %d", i, s.buffer_read_at, s.buffer[s.buffer_read_at], prev,
+              s.buffer[prev], multiplier * delta);
+    this->temp_.push_back(multiplier * delta);
+    prev = s.buffer_read_at;
+    s.buffer_read_at = (s.buffer_read_at + 1) % s.buffer_size;
+    multiplier *= -1;
+  }
+  s.buffer_read_at = (s.buffer_size + s.buffer_read_at - 1) % s.buffer_size;
+  this->temp_.push_back(this->idle_us_ * multiplier);
+
+  this->call_listeners_dumpers_();
+}
+
+}  // namespace remote_receiver
+}  // namespace esphome
+
+#endif