🏗 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/my9231/my9231.h

@@ -0,0 +1,64 @@
+#pragma once
+
+#include "esphome/core/component.h"
+#include "esphome/components/output/float_output.h"
+
+namespace esphome {
+namespace my9231 {
+
+/// MY9231 float output component.
+class MY9231OutputComponent : public Component {
+ public:
+  class Channel;
+  /** Construct the component.
+   *
+   * @param pin_di The pin which DI is connected to.
+   * @param pin_dcki The pin which DCKI is connected to.
+   */
+  MY9231OutputComponent(GPIOPin *pin_di, GPIOPin *pin_dcki) : pin_di_(pin_di), pin_dcki_(pin_dcki) {}
+
+  void set_num_channels(uint16_t num_channels) { this->num_channels_ = num_channels; }
+  void set_num_chips(uint8_t num_chips) { this->num_chips_ = num_chips; }
+  void set_bit_depth(uint8_t bit_depth) { this->bit_depth_ = bit_depth; }
+
+  /// Setup the MY9231.
+  void setup() override;
+  void dump_config() override;
+  /// HARDWARE setup_priority
+  float get_setup_priority() const override { return setup_priority::HARDWARE; }
+  /// Send new values if they were updated.
+  void loop() override;
+
+  class Channel : public output::FloatOutput {
+   public:
+    Channel(MY9231OutputComponent *parent, uint8_t channel) : parent_(parent), channel_(channel) {}
+
+   protected:
+    void write_state(float state) override {
+      auto amount = uint16_t(state * this->parent_->get_max_amount_());
+      this->parent_->set_channel_value_(this->channel_, amount);
+    }
+
+    MY9231OutputComponent *parent_;
+    uint8_t channel_;
+  };
+
+ protected:
+  uint16_t get_max_amount_() const { return (uint32_t(1) << this->bit_depth_) - 1; }
+
+  void set_channel_value_(uint8_t channel, uint16_t value);
+  void init_chips_(uint8_t command);
+  void write_word_(uint16_t value, uint8_t bits);
+  void send_di_pulses_(uint8_t count);
+
+  GPIOPin *pin_di_;
+  GPIOPin *pin_dcki_;
+  uint8_t bit_depth_;
+  uint16_t num_channels_;
+  uint8_t num_chips_;
+  std::vector<uint16_t> pwm_amounts_;
+  bool update_{true};
+};
+
+}  // namespace my9231
+}  // namespace esphome