🏗 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/lcd_base/lcd_display.h

@@ -0,0 +1,67 @@
+#pragma once
+
+#include "esphome/core/component.h"
+#include "esphome/core/defines.h"
+
+#ifdef USE_TIME
+#include "esphome/components/time/real_time_clock.h"
+#endif
+
+namespace esphome {
+namespace lcd_base {
+
+class LCDDisplay;
+
+using lcd_writer_t = std::function<void(LCDDisplay &)>;
+
+class LCDDisplay : public PollingComponent {
+ public:
+  LCDDisplay(uint32_t update_interval) : PollingComponent(update_interval) {}
+
+  void set_writer(lcd_writer_t &&writer) { this->writer_ = std::move(writer); }
+  void set_dimensions(uint8_t columns, uint8_t rows) {
+    this->columns_ = columns;
+    this->rows_ = rows;
+  }
+
+  void setup() override;
+  float get_setup_priority() const override;
+  void update() override;
+  void display();
+
+  /// Print the given text at the specified column and row.
+  void print(uint8_t column, uint8_t row, const char *str);
+  /// Print the given string at the specified column and row.
+  void print(uint8_t column, uint8_t row, const std::string &str);
+  /// Print the given text at column=0 and row=0.
+  void print(const char *str);
+  /// Print the given string at column=0 and row=0.
+  void print(const std::string &str);
+  /// Evaluate the printf-format and print the text at the specified column and row.
+  void printf(uint8_t column, uint8_t row, const char *format, ...) __attribute__((format(printf, 4, 5)));
+  /// Evaluate the printf-format and print the text at column=0 and row=0.
+  void printf(const char *format, ...) __attribute__((format(printf, 2, 3)));
+
+#ifdef USE_TIME
+  /// Evaluate the strftime-format and print the text at the specified column and row.
+  void strftime(uint8_t column, uint8_t row, const char *format, time::ESPTime time)
+      __attribute__((format(strftime, 4, 0)));
+  /// Evaluate the strftime-format and print the text at column=0 and row=0.
+  void strftime(const char *format, time::ESPTime time) __attribute__((format(strftime, 2, 0)));
+#endif
+
+ protected:
+  virtual bool is_four_bit_mode() = 0;
+  virtual void write_n_bits(uint8_t value, uint8_t n) = 0;
+  virtual void send(uint8_t value, bool rs) = 0;
+
+  void command_(uint8_t value);
+
+  uint8_t columns_;
+  uint8_t rows_;
+  uint8_t *buffer_{nullptr};
+  lcd_writer_t writer_;
+};
+
+}  // namespace lcd_base
+}  // namespace esphome