🏗 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/binary_sensor/binary_sensor.cpp

@@ -0,0 +1,71 @@
+#include "esphome/components/binary_sensor/binary_sensor.h"
+#include "esphome/core/log.h"
+
+namespace esphome {
+
+namespace binary_sensor {
+
+static const char *TAG = "binary_sensor";
+
+void BinarySensor::add_on_state_callback(std::function<void(bool)> &&callback) {
+  this->state_callback_.add(std::move(callback));
+}
+
+void BinarySensor::publish_state(bool state) {
+  if (!this->publish_dedup_.next(state))
+    return;
+  if (this->filter_list_ == nullptr) {
+    this->send_state_internal(state, false);
+  } else {
+    this->filter_list_->input(state, false);
+  }
+}
+void BinarySensor::publish_initial_state(bool state) {
+  if (!this->publish_dedup_.next(state))
+    return;
+  if (this->filter_list_ == nullptr) {
+    this->send_state_internal(state, true);
+  } else {
+    this->filter_list_->input(state, true);
+  }
+}
+void BinarySensor::send_state_internal(bool state, bool is_initial) {
+  ESP_LOGD(TAG, "'%s': Sending state %s", this->get_name().c_str(), state ? "ON" : "OFF");
+  this->has_state_ = true;
+  this->state = state;
+  if (!is_initial) {
+    this->state_callback_.call(state);
+  }
+}
+std::string BinarySensor::device_class() { return ""; }
+BinarySensor::BinarySensor(const std::string &name) : Nameable(name), state(false) {}
+BinarySensor::BinarySensor() : BinarySensor("") {}
+void BinarySensor::set_device_class(const std::string &device_class) { this->device_class_ = device_class; }
+std::string BinarySensor::get_device_class() {
+  if (this->device_class_.has_value())
+    return *this->device_class_;
+  return this->device_class();
+}
+void BinarySensor::add_filter(Filter *filter) {
+  filter->parent_ = this;
+  if (this->filter_list_ == nullptr) {
+    this->filter_list_ = filter;
+  } else {
+    Filter *last_filter = this->filter_list_;
+    while (last_filter->next_ != nullptr)
+      last_filter = last_filter->next_;
+    last_filter->next_ = filter;
+  }
+}
+void BinarySensor::add_filters(std::vector<Filter *> filters) {
+  for (Filter *filter : filters) {
+    this->add_filter(filter);
+  }
+}
+bool BinarySensor::has_state() const { return this->has_state_; }
+uint32_t BinarySensor::hash_base() { return 1210250844UL; }
+bool BinarySensor::is_status_binary_sensor() const { return false; }
+
+}  // namespace binary_sensor
+
+}  // namespace esphome