🏗 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/cpp_types.py

@@ -2,6 +2,7 @@ from esphome.cpp_generator import MockObj
 
 global_ns = MockObj('', '')
 void = global_ns.namespace('void')
+nullptr = global_ns.namespace('nullptr')
 float_ = global_ns.namespace('float')
 bool_ = global_ns.namespace('bool')
 std_ns = global_ns.namespace('std')
@@ -15,7 +16,6 @@ const_char_ptr = global_ns.namespace('const char *')
 NAN = global_ns.namespace('NAN')
 esphome_ns = global_ns  # using namespace esphome;
 App = esphome_ns.App
-io_ns = esphome_ns.namespace('io')
 Nameable = esphome_ns.class_('Nameable')
 Trigger = esphome_ns.class_('Trigger')
 Action = esphome_ns.class_('Action')
@@ -29,8 +29,5 @@ JsonObject = arduino_json_ns.class_('JsonObject')
 JsonObjectRef = JsonObject.operator('ref')
 JsonObjectConstRef = JsonObjectRef.operator('const')
 Controller = esphome_ns.class_('Controller')
-StoringController = esphome_ns.class_('StoringController', Controller)
 
 GPIOPin = esphome_ns.class_('GPIOPin')
-GPIOOutputPin = esphome_ns.class_('GPIOOutputPin', GPIOPin)
-GPIOInputPin = esphome_ns.class_('GPIOInputPin', GPIOPin)