🏗 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/rotary_encoder/sensor.py

@@ -0,0 +1,61 @@
+import esphome.codegen as cg
+import esphome.config_validation as cv
+from esphome import pins
+from esphome.components import sensor
+from esphome.const import CONF_ID, CONF_NAME, CONF_RESOLUTION, CONF_MIN_VALUE, CONF_MAX_VALUE
+
+rotary_encoder_ns = cg.esphome_ns.namespace('rotary_encoder')
+RotaryEncoderResolution = rotary_encoder_ns.enum('RotaryEncoderResolution')
+RESOLUTIONS = {
+    1: RotaryEncoderResolution.ROTARY_ENCODER_1_PULSE_PER_CYCLE,
+    2: RotaryEncoderResolution.ROTARY_ENCODER_2_PULSES_PER_CYCLE,
+    4: RotaryEncoderResolution.ROTARY_ENCODER_4_PULSES_PER_CYCLE,
+}
+
+CONF_PIN_A = 'pin_a'
+CONF_PIN_B = 'pin_b'
+CONF_PIN_RESET = 'pin_reset'
+
+RotaryEncoderSensor = rotary_encoder_ns.class_('RotaryEncoderSensor', sensor.Sensor, cg.Component)
+
+
+def validate_min_max_value(config):
+    if CONF_MIN_VALUE in config and CONF_MAX_VALUE in config:
+        min_val = config[CONF_MIN_VALUE]
+        max_val = config[CONF_MAX_VALUE]
+        if min_val >= max_val:
+            raise cv.Invalid("Max value {} must be smaller than min value {}"
+                             "".format(max_val, min_val))
+    return config
+
+
+CONFIG_SCHEMA = cv.nameable(sensor.SENSOR_SCHEMA.extend({
+    cv.GenerateID(): cv.declare_variable_id(RotaryEncoderSensor),
+    cv.Required(CONF_PIN_A): cv.All(pins.internal_gpio_input_pin_schema,
+                                    pins.validate_has_interrupt),
+    cv.Required(CONF_PIN_B): cv.All(pins.internal_gpio_input_pin_schema,
+                                    pins.validate_has_interrupt),
+    cv.Optional(CONF_PIN_RESET): pins.internal_gpio_input_pin_schema,
+    cv.Optional(CONF_RESOLUTION, default=1): cv.one_of(*RESOLUTIONS, int=True),
+    cv.Optional(CONF_MIN_VALUE): cv.int_,
+    cv.Optional(CONF_MAX_VALUE): cv.int_,
+}).extend(cv.COMPONENT_SCHEMA), validate_min_max_value)
+
+
+def to_code(config):
+    pin_a = yield cg.gpio_pin_expression(config[CONF_PIN_A])
+    pin_b = yield cg.gpio_pin_expression(config[CONF_PIN_B])
+    var = cg.new_Pvariable(config[CONF_ID], config[CONF_NAME], pin_a, pin_b)
+    yield cg.register_component(var, config)
+    yield sensor.register_sensor(var, config)
+
+    if CONF_PIN_RESET in config:
+        pin_i = yield cg.gpio_pin_expression(config[CONF_PIN_RESET])
+        cg.add(var.set_reset_pin(pin_i))
+    if CONF_RESOLUTION in config:
+        resolution = RESOLUTIONS[config[CONF_RESOLUTION]]
+        cg.add(var.set_resolution(resolution))
+    if CONF_MIN_VALUE in config:
+        cg.add(var.set_min_value(config[CONF_MIN_VALUE]))
+    if CONF_MAX_VALUE in config:
+        cg.add(var.set_max_value(config[CONF_MAX_VALUE]))