🏗 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/sensor/automation.h

@@ -0,0 +1,113 @@
+#pragma once
+
+#include "esphome/core/component.h"
+#include "esphome/core/automation.h"
+#include "esphome/components/sensor/sensor.h"
+
+namespace esphome {
+namespace sensor {
+
+class SensorStateTrigger : public Trigger<float> {
+ public:
+  explicit SensorStateTrigger(Sensor *parent) {
+    parent->add_on_state_callback([this](float value) { this->trigger(value); });
+  }
+};
+
+class SensorRawStateTrigger : public Trigger<float> {
+ public:
+  explicit SensorRawStateTrigger(Sensor *parent) {
+    parent->add_on_raw_state_callback([this](float value) { this->trigger(value); });
+  }
+};
+
+template<typename... Ts> class SensorPublishAction : public Action<Ts...> {
+ public:
+  SensorPublishAction(Sensor *sensor) : sensor_(sensor) {}
+  TEMPLATABLE_VALUE(float, state)
+  void play(Ts... x) override {
+    this->sensor_->publish_state(this->state_.value(x...));
+    this->play_next(x...);
+  }
+
+ protected:
+  Sensor *sensor_;
+};
+
+class ValueRangeTrigger : public Trigger<float>, public Component {
+ public:
+  explicit ValueRangeTrigger(Sensor *parent) : parent_(parent) {}
+
+  template<typename V> void set_min(V min) { this->min_ = min; }
+  template<typename V> void set_max(V max) { this->max_ = max; }
+
+  void setup() override {
+    this->rtc_ = global_preferences.make_preference<bool>(this->parent_->get_object_id_hash());
+    bool initial_state;
+    if (this->rtc_.load(&initial_state)) {
+      this->previous_in_range_ = initial_state;
+    }
+
+    this->parent_->add_on_state_callback([this](float state) { this->on_state_(state); });
+  }
+  float get_setup_priority() const override { return setup_priority::HARDWARE; }
+
+ protected:
+  void on_state_(float state) {
+    if (isnan(state))
+      return;
+
+    float local_min = this->min_.value(state);
+    float local_max = this->max_.value(state);
+
+    bool in_range;
+    if (isnan(local_min) && isnan(local_max)) {
+      in_range = this->previous_in_range_;
+    } else if (isnan(local_min)) {
+      in_range = state <= local_max;
+    } else if (isnan(local_max)) {
+      in_range = state >= local_min;
+    } else {
+      in_range = local_min <= state && state <= local_max;
+    }
+
+    if (in_range != this->previous_in_range_ && in_range) {
+      this->trigger(state);
+    }
+
+    this->previous_in_range_ = in_range;
+    this->rtc_.save(&in_range);
+  }
+
+  Sensor *parent_;
+  ESPPreferenceObject rtc_;
+  bool previous_in_range_{false};
+  TemplatableValue<float, float> min_{NAN};
+  TemplatableValue<float, float> max_{NAN};
+};
+
+template<typename... Ts> class SensorInRangeCondition : public Condition<Ts...> {
+ public:
+  SensorInRangeCondition(Sensor *parent) : parent_(parent) {}
+
+  void set_min(float min) { this->min_ = min; }
+  void set_max(float max) { this->max_ = max; }
+  bool check(Ts... x) override {
+    const float state = this->parent_->state;
+    if (isnan(this->min_)) {
+      return state <= this->max_;
+    } else if (isnan(this->max_)) {
+      return state >= this->min_;
+    } else {
+      return this->min_ <= state && state <= this->max_;
+    }
+  }
+
+ protected:
+  Sensor *parent_;
+  float min_{NAN};
+  float max_{NAN};
+};
+
+}  // namespace sensor
+}  // namespace esphome