🏗 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/bme680/sensor.py

@@ -0,0 +1,101 @@
+import esphome.codegen as cg
+import esphome.config_validation as cv
+from esphome import core
+from esphome.components import i2c, sensor
+from esphome.const import CONF_DURATION, CONF_GAS_RESISTANCE, CONF_HEATER, \
+    CONF_HUMIDITY, CONF_ID, CONF_IIR_FILTER, CONF_OVERSAMPLING, CONF_PRESSURE, \
+    CONF_TEMPERATURE, CONF_UPDATE_INTERVAL, UNIT_OHM, ICON_GAS_CYLINDER, UNIT_CELSIUS, \
+    ICON_THERMOMETER, UNIT_HECTOPASCAL, ICON_GAUGE, ICON_WATER_PERCENT, UNIT_PERCENT
+
+DEPENDENCIES = ['i2c']
+
+bme680_ns = cg.esphome_ns.namespace('bme680')
+BME680Oversampling = bme680_ns.enum('BME680Oversampling')
+OVERSAMPLING_OPTIONS = {
+    'NONE': BME680Oversampling.BME680_OVERSAMPLING_NONE,
+    '1X': BME680Oversampling.BME680_OVERSAMPLING_1X,
+    '2X': BME680Oversampling.BME680_OVERSAMPLING_2X,
+    '4X': BME680Oversampling.BME680_OVERSAMPLING_4X,
+    '8X': BME680Oversampling.BME680_OVERSAMPLING_8X,
+    '16X': BME680Oversampling.BME680_OVERSAMPLING_16X,
+}
+
+BME680IIRFilter = bme680_ns.enum('BME680IIRFilter')
+IIR_FILTER_OPTIONS = {
+    'OFF': BME680IIRFilter.BME680_IIR_FILTER_OFF,
+    '1X': BME680IIRFilter.BME680_IIR_FILTER_1X,
+    '3X': BME680IIRFilter.BME680_IIR_FILTER_3X,
+    '7X': BME680IIRFilter.BME680_IIR_FILTER_7X,
+    '15X': BME680IIRFilter.BME680_IIR_FILTER_15X,
+    '31X': BME680IIRFilter.BME680_IIR_FILTER_31X,
+    '63X': BME680IIRFilter.BME680_IIR_FILTER_63X,
+    '127X': BME680IIRFilter.BME680_IIR_FILTER_127X,
+}
+
+BME680Component = bme680_ns.class_('BME680Component', cg.PollingComponent, i2c.I2CDevice)
+
+CONFIG_SCHEMA = cv.Schema({
+    cv.GenerateID(): cv.declare_variable_id(BME680Component),
+    cv.Optional(CONF_TEMPERATURE): cv.nameable(
+        sensor.sensor_schema(UNIT_CELSIUS, ICON_THERMOMETER, 1).extend({
+            cv.Optional(CONF_OVERSAMPLING, default='16X'):
+                cv.one_of(*OVERSAMPLING_OPTIONS, upper=True),
+        })),
+    cv.Optional(CONF_PRESSURE): cv.nameable(
+        sensor.sensor_schema(UNIT_HECTOPASCAL, ICON_GAUGE, 1).extend({
+            cv.Optional(CONF_OVERSAMPLING, default='16X'):
+                cv.one_of(*OVERSAMPLING_OPTIONS, upper=True),
+        })),
+    cv.Optional(CONF_HUMIDITY): cv.nameable(
+        sensor.sensor_schema(UNIT_PERCENT, ICON_WATER_PERCENT, 1).extend({
+            cv.Optional(CONF_OVERSAMPLING, default='16X'):
+                cv.one_of(*OVERSAMPLING_OPTIONS, upper=True),
+        })),
+    cv.Optional(CONF_GAS_RESISTANCE): cv.nameable(
+        sensor.sensor_schema(UNIT_OHM, ICON_GAS_CYLINDER, 1)),
+    cv.Optional(CONF_IIR_FILTER, default='OFF'): cv.one_of(*IIR_FILTER_OPTIONS, upper=True),
+    cv.Optional(CONF_HEATER): cv.Any(None, cv.All(cv.Schema({
+        cv.Optional(CONF_TEMPERATURE, default=320): cv.All(cv.Coerce(int), cv.Range(200, 400)),
+        cv.Optional(CONF_DURATION, default='150ms'): cv.All(
+            cv.positive_time_period_milliseconds, cv.Range(max=core.TimePeriod(milliseconds=4032)))
+    }, cv.has_at_least_one_key(CONF_TEMPERATURE, CONF_DURATION)))),
+    cv.Optional(CONF_UPDATE_INTERVAL, default='60s'): cv.update_interval,
+}).extend(cv.COMPONENT_SCHEMA).extend(i2c.i2c_device_schema(0x76))
+
+
+def to_code(config):
+    var = cg.new_Pvariable(config[CONF_ID], config[CONF_UPDATE_INTERVAL])
+    yield cg.register_component(var, config)
+    yield i2c.register_i2c_device(var, config)
+
+    if CONF_TEMPERATURE in config:
+        conf = config[CONF_TEMPERATURE]
+        sens = yield sensor.new_sensor(conf)
+        cg.add(var.set_temperature_sensor(sens))
+        cg.add(var.set_temperature_oversampling(OVERSAMPLING_OPTIONS[conf[CONF_OVERSAMPLING]]))
+
+    if CONF_PRESSURE in config:
+        conf = config[CONF_PRESSURE]
+        sens = yield sensor.new_sensor(conf)
+        cg.add(var.set_pressure_sensor(sens))
+        cg.add(var.set_pressure_oversampling(OVERSAMPLING_OPTIONS[conf[CONF_OVERSAMPLING]]))
+
+    if CONF_HUMIDITY in config:
+        conf = config[CONF_HUMIDITY]
+        sens = yield sensor.new_sensor(conf)
+        cg.add(var.set_humidity_sensor(sens))
+        cg.add(var.set_humidity_oversampling(OVERSAMPLING_OPTIONS[conf[CONF_OVERSAMPLING]]))
+
+    if CONF_GAS_RESISTANCE in config:
+        conf = config[CONF_GAS_RESISTANCE]
+        sens = yield sensor.new_sensor(conf)
+        cg.add(var.set_gas_resistance_sensor(sens))
+
+    cg.add(var.set_iir_filter(IIR_FILTER_OPTIONS[config[CONF_IIR_FILTER]]))
+
+    if CONF_HEATER in config:
+        conf = config[CONF_HEATER]
+        if not conf:
+            cg.add(var.set_heater(0, 0))
+        else:
+            cg.add(var.set_heater(conf[CONF_TEMPERATURE], conf[CONF_DURATION]))