🏗 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/ledc/ledc_output.cpp

@@ -0,0 +1,44 @@
+#include "ledc_output.h"
+#include "esphome/core/log.h"
+
+#ifdef ARDUINO_ARCH_ESP32
+
+#include <esp32-hal-ledc.h>
+
+namespace esphome {
+namespace ledc {
+
+static const char *TAG = "ledc.output";
+
+void LEDCOutput::write_state(float state) {
+  if (this->pin_->is_inverted()) {
+    state = 1.0f - state;
+  }
+
+  const uint32_t max_duty = (uint32_t(1) << this->bit_depth_) - 1;
+  const float duty_rounded = roundf(state * max_duty);
+  auto duty = static_cast<uint32_t>(duty_rounded);
+  ledcWrite(this->channel_, duty);
+}
+
+void LEDCOutput::setup() {
+  ledcSetup(this->channel_, this->frequency_, this->bit_depth_);
+  ledcAttachPin(this->pin_->get_pin(), this->channel_);
+
+  this->turn_off();
+}
+
+void LEDCOutput::dump_config() {
+  ESP_LOGCONFIG(TAG, "LEDC Output:");
+  LOG_PIN("  Pin", this->pin_);
+  ESP_LOGCONFIG(TAG, "  LEDC Channel: %u", this->channel_);
+  ESP_LOGCONFIG(TAG, "  Frequency: %.1f Hz", this->frequency_);
+  ESP_LOGCONFIG(TAG, "  Bit Depth: %u", this->bit_depth_);
+}
+
+uint8_t next_ledc_channel = 0;
+
+}  // namespace ledc
+}  // namespace esphome
+
+#endif

esphome/components/ledc/ledc_output.h

@@ -0,0 +1,43 @@
+#pragma once
+
+#include "esphome/core/component.h"
+#include "esphome/core/esphal.h"
+#include "esphome/components/output/float_output.h"
+
+#ifdef ARDUINO_ARCH_ESP32
+
+namespace esphome {
+namespace ledc {
+
+class LEDCOutput : public output::FloatOutput, public Component {
+ public:
+  explicit LEDCOutput(GPIOPin *pin) : pin_(pin) {}
+
+  void set_channel(uint8_t channel) { this->channel_ = channel; }
+  void set_bit_depth(uint8_t bit_depth) { this->bit_depth_ = bit_depth; }
+  void set_frequency(float frequency) { this->frequency_ = frequency; }
+
+  // ========== INTERNAL METHODS ==========
+  // (In most use cases you won't need these)
+  /// Setup LEDC.
+  void setup() override;
+  void dump_config() override;
+  /// HARDWARE setup priority
+  float get_setup_priority() const override { return setup_priority::HARDWARE; }
+
+  /// Override FloatOutput's write_state.
+  void write_state(float adjusted_value) override;
+
+ protected:
+  GPIOPin *pin_;
+  uint8_t channel_{};
+  uint8_t bit_depth_{};
+  float frequency_{};
+};
+
+extern uint8_t next_ledc_channel;
+
+}  // namespace ledc
+}  // namespace esphome
+
+#endif

esphome/components/ledc/output.py

@@ -0,0 +1,39 @@
+
+from esphome import pins
+from esphome.components import output
+import esphome.config_validation as cv
+import esphome.codegen as cg
+from esphome.const import APB_CLOCK_FREQ, CONF_BIT_DEPTH, CONF_CHANNEL, CONF_FREQUENCY, \
+    CONF_ID, CONF_PIN, ESP_PLATFORM_ESP32
+
+ESP_PLATFORMS = [ESP_PLATFORM_ESP32]
+
+
+def validate_frequency_bit_depth(obj):
+    frequency = obj.get(CONF_FREQUENCY, 1000)
+    bit_depth = obj.get(CONF_BIT_DEPTH, 12)
+    max_freq = APB_CLOCK_FREQ / (2**bit_depth)
+    if frequency > max_freq:
+        raise cv.Invalid('Maximum frequency for bit depth {} is {}Hz'.format(bit_depth, max_freq))
+    return obj
+
+
+ledc_ns = cg.esphome_ns.namespace('ledc')
+LEDCOutput = ledc_ns.class_('LEDCOutput', output.FloatOutput, cg.Component)
+
+CONFIG_SCHEMA = cv.All(output.FLOAT_OUTPUT_SCHEMA.extend({
+    cv.Required(CONF_ID): cv.declare_variable_id(LEDCOutput),
+    cv.Required(CONF_PIN): pins.internal_gpio_output_pin_schema,
+    cv.Optional(CONF_FREQUENCY, default='1kHz'): cv.frequency,
+    cv.Optional(CONF_BIT_DEPTH, default=12): cv.All(cv.int_, cv.Range(min=1, max=15)),
+    cv.Optional(CONF_CHANNEL): cv.All(cv.int_, cv.Range(min=0, max=15))
+}).extend(cv.COMPONENT_SCHEMA), validate_frequency_bit_depth)
+
+
+def to_code(config):
+    gpio = yield cg.gpio_pin_expression(config[CONF_PIN])
+    var = cg.new_Pvariable(config[CONF_ID], gpio)
+    yield cg.register_component(var, config)
+    yield output.register_output(var, config)
+    if CONF_CHANNEL in config:
+        cg.add(var.set_channel(config[CONF_CHANNEL]))