🏗 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/esp32_camera/esp32_camera.h

@@ -0,0 +1,113 @@
+#pragma once
+
+#ifdef ARDUINO_ARCH_ESP32
+
+#include "esphome/core/component.h"
+#include "esphome/core/helpers.h"
+#include <esp_camera.h>
+
+namespace esphome {
+namespace esp32_camera {
+
+class ESP32Camera;
+
+class CameraImage {
+ public:
+  CameraImage(camera_fb_t *buffer);
+  camera_fb_t *get_raw_buffer();
+  uint8_t *get_data_buffer();
+  size_t get_data_length();
+
+ protected:
+  camera_fb_t *buffer_;
+};
+
+class CameraImageReader {
+ public:
+  void set_image(std::shared_ptr<CameraImage> image);
+  size_t available() const;
+  uint8_t *peek_data_buffer();
+  void consume_data(size_t consumed);
+  void return_image();
+
+ protected:
+  std::shared_ptr<CameraImage> image_;
+  size_t offset_{0};
+};
+
+enum ESP32CameraFrameSize {
+  ESP32_CAMERA_SIZE_160X120,    // QQVGA
+  ESP32_CAMERA_SIZE_128X160,    // QQVGA2
+  ESP32_CAMERA_SIZE_176X144,    // QCIF
+  ESP32_CAMERA_SIZE_240X176,    // HQVGA
+  ESP32_CAMERA_SIZE_320X240,    // QVGA
+  ESP32_CAMERA_SIZE_400X296,    // CIF
+  ESP32_CAMERA_SIZE_640X480,    // VGA
+  ESP32_CAMERA_SIZE_800X600,    // SVGA
+  ESP32_CAMERA_SIZE_1024X768,   // XGA
+  ESP32_CAMERA_SIZE_1280X1024,  // SXGA
+  ESP32_CAMERA_SIZE_1600X1200,  // UXGA
+};
+
+class ESP32Camera : public Component, public Nameable {
+ public:
+  ESP32Camera(const std::string &name);
+  void set_data_pins(std::array<uint8_t, 8> pins);
+  void set_vsync_pin(uint8_t pin);
+  void set_href_pin(uint8_t pin);
+  void set_pixel_clock_pin(uint8_t pin);
+  void set_external_clock(uint8_t pin, uint32_t frequency);
+  void set_i2c_pins(uint8_t sda, uint8_t scl);
+  void set_frame_size(ESP32CameraFrameSize size);
+  void set_jpeg_quality(uint8_t quality);
+  void set_reset_pin(uint8_t pin);
+  void set_power_down_pin(uint8_t pin);
+  void set_vertical_flip(bool vertical_flip);
+  void set_horizontal_mirror(bool horizontal_mirror);
+  void set_contrast(int contrast);
+  void set_brightness(int brightness);
+  void set_saturation(int saturation);
+  void set_max_update_interval(uint32_t max_update_interval);
+  void set_idle_update_interval(uint32_t idle_update_interval);
+  void set_test_pattern(bool test_pattern);
+  void setup() override;
+  void loop() override;
+  void dump_config() override;
+  void add_image_callback(std::function<void(std::shared_ptr<CameraImage>)> &&f);
+  float get_setup_priority() const override;
+  void request_stream();
+  void request_image();
+
+ protected:
+  uint32_t hash_base() override;
+  bool has_requested_image_() const;
+  bool can_return_image_() const;
+
+  static void framebuffer_task(void *pv);
+
+  camera_config_t config_{};
+  bool vertical_flip_{true};
+  bool horizontal_mirror_{true};
+  int contrast_{0};
+  int brightness_{0};
+  int saturation_{0};
+  bool test_pattern_{false};
+
+  esp_err_t init_error_{ESP_OK};
+  std::shared_ptr<CameraImage> current_image_;
+  uint32_t last_stream_request_{0};
+  bool single_requester_{false};
+  QueueHandle_t framebuffer_get_queue_;
+  QueueHandle_t framebuffer_return_queue_;
+  CallbackManager<void(std::shared_ptr<CameraImage>)> new_image_callback_;
+  uint32_t max_update_interval_{1000};
+  uint32_t idle_update_interval_{15000};
+  uint32_t last_update_{0};
+};
+
+extern ESP32Camera *global_esp32_camera;
+
+}  // namespace esp32_camera
+}  // namespace esphome
+
+#endif