🏗 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/sds011/sensor.py

@@ -0,0 +1,54 @@
+import esphome.codegen as cg
+import esphome.config_validation as cv
+from esphome.components import sensor, uart
+from esphome.const import (CONF_ID, CONF_PM_10_0, CONF_PM_2_5, CONF_RX_ONLY,
+                           CONF_UPDATE_INTERVAL, UNIT_MICROGRAMS_PER_CUBIC_METER,
+                           ICON_CHEMICAL_WEAPON)
+
+DEPENDENCIES = ['uart']
+
+sds011_ns = cg.esphome_ns.namespace('sds011')
+SDS011Component = sds011_ns.class_('SDS011Component', uart.UARTDevice, cg.Component)
+
+
+def validate_sds011_rx_mode(value):
+    if CONF_UPDATE_INTERVAL in value and not value.get(CONF_RX_ONLY):
+        update_interval = value[CONF_UPDATE_INTERVAL]
+        if update_interval.total_minutes > 30:
+            raise cv.Invalid("Maximum update interval is 30min")
+    elif value.get(CONF_RX_ONLY) and CONF_UPDATE_INTERVAL in value:
+        # update_interval does not affect anything in rx-only mode, let's warn user about
+        # that
+        raise cv.Invalid("update_interval has no effect in rx_only mode. Please remove it.",
+                         path=['update_interval'])
+    return value
+
+
+CONFIG_SCHEMA = cv.All(cv.Schema({
+    cv.GenerateID(): cv.declare_variable_id(SDS011Component),
+
+    cv.Optional(CONF_PM_2_5):
+        cv.nameable(sensor.sensor_schema(UNIT_MICROGRAMS_PER_CUBIC_METER, ICON_CHEMICAL_WEAPON, 1)),
+    cv.Optional(CONF_PM_10_0):
+        cv.nameable(sensor.sensor_schema(UNIT_MICROGRAMS_PER_CUBIC_METER, ICON_CHEMICAL_WEAPON, 1)),
+
+    cv.Optional(CONF_RX_ONLY, default=False): cv.boolean,
+    cv.Optional(CONF_UPDATE_INTERVAL, default='0min'): cv.positive_time_period_minutes,
+}).extend(cv.COMPONENT_SCHEMA).extend(uart.UART_DEVICE_SCHEMA), validate_sds011_rx_mode)
+
+
+def to_code(config):
+    var = cg.new_Pvariable(config[CONF_ID])
+    yield cg.register_component(var, config)
+    yield uart.register_uart_device(var, config)
+
+    cg.add(var.set_update_interval_min(config[CONF_UPDATE_INTERVAL]))
+    cg.add(var.set_rx_mode_only(config[CONF_RX_ONLY]))
+
+    if CONF_PM_2_5 in config:
+        sens = yield sensor.new_sensor(config[CONF_PM_2_5])
+        cg.add(var.set_pm_2_5_sensor(sens))
+
+    if CONF_PM_10_0 in config:
+        sens = yield sensor.new_sensor(config[CONF_PM_10_0])
+        cg.add(var.set_pm_10_0_sensor(sens))