🏗 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/uart/switch/__init__.py

@@ -0,0 +1,38 @@
+import esphome.codegen as cg
+import esphome.config_validation as cv
+from esphome.components import switch, uart
+from esphome.const import CONF_DATA, CONF_ID, CONF_INVERTED, CONF_NAME
+from esphome.core import HexInt
+from esphome.py_compat import text_type, binary_type, char_to_byte
+from .. import uart_ns
+
+DEPENDENCIES = ['uart']
+
+UARTSwitch = uart_ns.class_('UARTSwitch', switch.Switch, uart.UARTDevice)
+
+
+def validate_data(value):
+    if isinstance(value, text_type):
+        return value.encode('utf-8')
+    if isinstance(value, str):
+        return value
+    if isinstance(value, list):
+        return cv.Schema([cv.hex_uint8_t])(value)
+    raise cv.Invalid("data must either be a string wrapped in quotes or a list of bytes")
+
+
+CONFIG_SCHEMA = cv.nameable(switch.SWITCH_SCHEMA.extend({
+    cv.GenerateID(): cv.declare_variable_id(UARTSwitch),
+    cv.Required(CONF_DATA): validate_data,
+    cv.Optional(CONF_INVERTED): cv.invalid("UART switches do not support inverted mode!"),
+}).extend(uart.UART_DEVICE_SCHEMA))
+
+
+def to_code(config):
+    data = config[CONF_DATA]
+    if isinstance(data, binary_type):
+        data = [HexInt(char_to_byte(x)) for x in data]
+    var = cg.new_Pvariable(config[CONF_ID], config[CONF_NAME], data)
+    yield cg.register_component(var, config)
+    yield switch.register_switch(var, config)
+    yield uart.register_uart_device(var, config)