🏗 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/core/log.cpp

@@ -0,0 +1,67 @@
+#include "esphome/core/log.h"
+#include "esphome/core/defines.h"
+#include "esphome/core/helpers.h"
+
+#ifdef USE_LOGGER
+#include "esphome/components/logger/logger.h"
+#endif
+
+namespace esphome {
+
+int HOT esp_log_printf_(int level, const char *tag, const char *format, ...) {  // NOLINT
+  va_list arg;
+  va_start(arg, format);
+  int ret = esp_log_vprintf_(level, tag, format, arg);
+  va_end(arg);
+  return ret;
+}
+#ifdef USE_STORE_LOG_STR_IN_FLASH
+int HOT esp_log_printf_(int level, const char *tag, const __FlashStringHelper *format, ...) {
+  va_list arg;
+  va_start(arg, format);
+  int ret = esp_log_vprintf_(level, tag, format, arg);
+  va_end(arg);
+  return ret;
+  return 0;
+}
+#endif
+
+int HOT esp_log_vprintf_(int level, const char *tag, const char *format, va_list args) {  // NOLINT
+#ifdef USE_LOGGER
+  auto *log = logger::global_logger;
+  if (log == nullptr)
+    return 0;
+
+  return log->log_vprintf_(level, tag, format, args);
+#else
+  return 0;
+#endif
+}
+
+#ifdef USE_STORE_LOG_STR_IN_FLASH
+int HOT esp_log_vprintf_(int level, const char *tag, const __FlashStringHelper *format, va_list args) {  // NOLINT
+#ifdef USE_LOGGER
+  auto *log = logger::global_logger;
+  if (log == nullptr)
+    return 0;
+
+  return log->log_vprintf_(level, tag, format, args);
+#else
+  return 0;
+#endif
+}
+#endif
+
+int HOT esp_idf_log_vprintf_(const char *format, va_list args) {  // NOLINT
+#ifdef USE_LOGGER
+  auto *log = logger::global_logger;
+  if (log == nullptr)
+    return 0;
+
+  return log->log_vprintf_(log->get_global_log_level(), "", format, args);
+#else
+  return 0;
+#endif
+}
+
+}  // namespace esphome