🏗 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/platformio_api.py

@@ -12,6 +12,50 @@ from esphome.util import run_external_command, run_external_process
 _LOGGER = logging.getLogger(__name__)
 
 
+def patch_structhash():
+    # Patch platformio's structhash to not recompile the entire project when files are
+    # removed/added. This might have unintended consequences, but this improves compile
+    # times greatly when adding/removing components and a simple clean build solves
+    # all issues
+    from platformio.commands import run
+    from platformio import util
+    from os.path import join, isdir, getmtime, isfile
+    from os import makedirs
+
+    def patched_clean_build_dir(build_dir):
+        structhash_file = join(build_dir, "structure.hash")
+        platformio_ini = join(util.get_project_dir(), "platformio.ini")
+
+        # if project's config is modified
+        if isdir(build_dir) and getmtime(platformio_ini) > getmtime(build_dir):
+            util.rmtree_(build_dir)
+
+        if not isdir(build_dir):
+            makedirs(build_dir)
+
+        proj_hash = run.calculate_project_hash()
+
+        # check project structure
+        if isdir(build_dir) and isfile(structhash_file):
+            with open(structhash_file) as f:
+                if f.read() == proj_hash:
+                    return
+
+        with open(structhash_file, "w") as f:
+            f.write(proj_hash)
+
+    # pylint: disable=protected-access
+    orig = run._clean_build_dir
+
+    def patched_safe(*args, **kwargs):
+        try:
+            return patched_clean_build_dir(*args, **kwargs)
+        except Exception:  # pylint: disable=broad-except
+            return orig(*args, **kwargs)
+
+    run._clean_build_dir = patched_safe
+
+
 def run_platformio_cli(*args, **kwargs):
     os.environ["PLATFORMIO_FORCE_COLOR"] = "true"
     os.environ["PLATFORMIO_BUILD_DIR"] = os.path.abspath(CORE.relative_pioenvs_path())
@@ -20,6 +64,11 @@ def run_platformio_cli(*args, **kwargs):
 
     if os.environ.get('ESPHOME_USE_SUBPROCESS') is None:
         import platformio.__main__
+        try:
+            patch_structhash()
+        except Exception:  # pylint: disable=broad-except
+            # Ignore when patch fails
+            pass
         return run_external_command(platformio.__main__.main,
                                     *cmd, **kwargs)