🏗 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/my9231/output.py

@@ -0,0 +1,23 @@
+import esphome.codegen as cg
+import esphome.config_validation as cv
+from esphome.components import output
+from esphome.components.my9231 import MY9231OutputComponent
+from esphome.const import CONF_CHANNEL, CONF_ID
+
+DEPENDENCIES = ['my9231']
+
+Channel = MY9231OutputComponent.class_('Channel', output.FloatOutput)
+
+CONF_MY9231_ID = 'my9231_id'
+CONFIG_SCHEMA = output.FLOAT_OUTPUT_SCHEMA.extend({
+    cv.GenerateID(CONF_MY9231_ID): cv.use_variable_id(MY9231OutputComponent),
+
+    cv.Required(CONF_ID): cv.declare_variable_id(Channel),
+    cv.Required(CONF_CHANNEL): cv.All(cv.int_, cv.Range(min=0, max=65535)),
+}).extend(cv.COMPONENT_SCHEMA)
+
+
+def to_code(config):
+    my9231 = yield cg.get_variable(config[CONF_MY9231_ID])
+    var = cg.new_Pvariable(config[CONF_ID], my9231, config[CONF_CHANNEL])
+    yield output.register_output(var, config)