🏗 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).

script/clang-format.py

@@ -0,0 +1,164 @@
+#!/usr/bin/env python
+
+from __future__ import print_function
+
+import multiprocessing
+import os
+import re
+import subprocess
+import sys
+
+import argparse
+import click
+import threading
+
+is_py2 = sys.version[0] == '2'
+
+if is_py2:
+    import Queue as queue
+else:
+    import queue as queue
+
+root_path = os.path.abspath(os.path.normpath(os.path.join(__file__, '..', '..')))
+basepath = os.path.join(root_path, 'esphome')
+rel_basepath = os.path.relpath(basepath, os.getcwd())
+
+
+def run_format(args, queue, lock):
+    """Takes filenames out of queue and runs clang-tidy on them."""
+    while True:
+        path = queue.get()
+        invocation = ['clang-format-7']
+        if args.inplace:
+            invocation.append('-i')
+        invocation.append(path)
+
+        proc = subprocess.Popen(invocation, stdout=subprocess.PIPE,
+                                stderr=subprocess.PIPE)
+        output, err = proc.communicate()
+        with lock:
+            if proc.returncode != 0:
+                print(' '.join(invocation))
+                print(output.decode('utf-8'))
+                print(err.decode('utf-8'))
+        queue.task_done()
+
+
+def progress_bar_show(value):
+    if value is None:
+        return ''
+    return value
+
+
+def walk_files(path):
+    for root, _, files in os.walk(path):
+        for name in files:
+            yield os.path.join(root, name)
+
+
+def get_output(*args):
+    proc = subprocess.Popen(args, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
+    output, err = proc.communicate()
+    return output.decode('utf-8')
+
+
+def splitlines_no_ends(string):
+    return [s.strip() for s in string.splitlines()]
+
+
+def filter_changed(files):
+    for remote in ('upstream', 'origin'):
+        command = ['git', 'merge-base', '{}/dev'.format(remote), 'HEAD']
+        try:
+            merge_base = splitlines_no_ends(get_output(*command))[0]
+            break
+        except:
+            pass
+    else:
+        return files
+    command = ['git', 'diff', merge_base, '--name-only']
+    changed = splitlines_no_ends(get_output(*command))
+    changed = {os.path.relpath(f, os.getcwd()) for f in changed}
+    print("Changed Files:")
+    files = [p for p in files if p in changed]
+    for p in files:
+        print("  {}".format(p))
+    if not files:
+        print("  No changed files")
+    return files
+
+
+def main():
+    parser = argparse.ArgumentParser()
+    parser.add_argument('-j', '--jobs', type=int,
+                        default=multiprocessing.cpu_count(),
+                        help='number of tidy instances to be run in parallel.')
+    parser.add_argument('files', nargs='*', default=[],
+                        help='files to be processed (regex on path)')
+    parser.add_argument('-i', '--inplace', action='store_true',
+                        help='apply fix-its')
+    parser.add_argument('-q', '--quiet', action='store_false',
+                        help='Run clang-tidy in quiet mode')
+    parser.add_argument('-c', '--changed', action='store_true',
+                        help='Only run on changed files')
+    args = parser.parse_args()
+
+    try:
+        get_output('clang-format-7', '-version')
+    except:
+        print("""
+        Oops. It looks like clang-format is not installed. 
+        
+        Please check you can run "clang-format-7 -version" in your terminal and install
+        clang-format (v7) if necessary.
+        
+        Note you can also upload your code as a pull request on GitHub and see the CI check
+        output to apply clang-format.
+        """)
+        return 1
+
+    files = []
+    for path in walk_files(basepath):
+        filetypes = ('.cpp', '.h', '.tcc')
+        ext = os.path.splitext(path)[1]
+        if ext in filetypes:
+            path = os.path.relpath(path, os.getcwd())
+            files.append(path)
+    # Match against re
+    file_name_re = re.compile('|'.join(args.files))
+    files = [p for p in files if file_name_re.search(p)]
+
+    if args.changed:
+        files = filter_changed(files)
+
+    files.sort()
+
+    return_code = 0
+    try:
+        task_queue = queue.Queue(args.jobs)
+        lock = threading.Lock()
+        for _ in range(args.jobs):
+            t = threading.Thread(target=run_format,
+                                 args=(args, task_queue, lock))
+            t.daemon = True
+            t.start()
+
+        # Fill the queue with files.
+        with click.progressbar(files, width=30, file=sys.stderr,
+                               item_show_func=progress_bar_show) as bar:
+            for name in bar:
+                task_queue.put(name)
+
+        # Wait for all threads to be done.
+        task_queue.join()
+
+    except KeyboardInterrupt:
+        print()
+        print('Ctrl-C detected, goodbye.')
+        os.kill(0, 9)
+
+    sys.exit(return_code)
+
+
+if __name__ == '__main__':
+    main()