🏗 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/status/binary_sensor.py

@@ -0,0 +1,20 @@
+from esphome.components import binary_sensor
+import esphome.config_validation as cv
+import esphome.codegen as cg
+from esphome.const import CONF_ID, CONF_NAME, CONF_DEVICE_CLASS, DEVICE_CLASS_CONNECTIVITY
+
+status_ns = cg.esphome_ns.namespace('status')
+StatusBinarySensor = status_ns.class_('StatusBinarySensor', binary_sensor.BinarySensor,
+                                      cg.Component)
+
+CONFIG_SCHEMA = cv.nameable(binary_sensor.BINARY_SENSOR_SCHEMA.extend({
+    cv.GenerateID(): cv.declare_variable_id(StatusBinarySensor),
+
+    cv.Optional(CONF_DEVICE_CLASS, default=DEVICE_CLASS_CONNECTIVITY): binary_sensor.device_class,
+}).extend(cv.COMPONENT_SCHEMA))
+
+
+def to_code(config):
+    var = cg.new_Pvariable(config[CONF_ID], config[CONF_NAME])
+    yield cg.register_component(var, config)
+    yield binary_sensor.register_binary_sensor(var, config)

esphome/components/status/status_binary_sensor.cpp

@@ -0,0 +1,40 @@
+#include "status_binary_sensor.h"
+#include "esphome/core/log.h"
+#include "esphome/core/util.h"
+
+#ifdef USE_MQTT
+#include "esphome/components/mqtt/mqtt_client.h"
+#endif
+#ifdef USE_API
+#include "esphome/components/api/api_server.h"
+#endif
+
+namespace esphome {
+namespace status {
+
+static const char *TAG = "status";
+
+StatusBinarySensor::StatusBinarySensor(const std::string &name) : BinarySensor(name) {}
+void StatusBinarySensor::loop() {
+  bool status = network_is_connected();
+#ifdef USE_MQTT
+  if (mqtt::global_mqtt_client != nullptr) {
+    status = mqtt::global_mqtt_client->is_connected();
+  }
+#endif
+#ifdef USE_API
+  if (api::global_api_server != nullptr) {
+    status = api::global_api_server->is_connected();
+  }
+#endif
+
+  if (this->last_status_ != status) {
+    this->publish_state(status);
+    this->last_status_ = status;
+  }
+}
+void StatusBinarySensor::setup() { this->publish_state(false); }
+void StatusBinarySensor::dump_config() { LOG_BINARY_SENSOR("", "Status Binary Sensor", this); }
+
+}  // namespace status
+}  // namespace esphome

esphome/components/status/status_binary_sensor.h

@@ -0,0 +1,28 @@
+#pragma once
+
+#include "esphome/core/component.h"
+#include "esphome/components/binary_sensor/binary_sensor.h"
+
+namespace esphome {
+namespace status {
+
+class StatusBinarySensor : public binary_sensor::BinarySensor, public Component {
+ public:
+  /// Construct the status binary sensor
+  explicit StatusBinarySensor(const std::string &name);
+
+  void loop() override;
+
+  void setup() override;
+  void dump_config() override;
+
+  float get_setup_priority() const override { return setup_priority::DATA; }
+
+  bool is_status_binary_sensor() const override { return true; }
+
+ protected:
+  bool last_status_{false};
+};
+
+}  // namespace status
+}  // namespace esphome