New component: Python Script (#7950)

* Add initial version

* Fix requirements

* Prefer logging over printing

* Set executor thread name on >Py36 only

* Add tests

* Lint

* Add restrictedpython to test dependencies

* Create python_script.py

From doc:
```
However, an empty dict ({}) is treated as is. If you want to specify a list that can contain anything, specify it as dict:
>>> schema = Schema({}, extra=ALLOW_EXTRA)  # don't do this
>>> try:
...   schema({'extra': 1})
...   raise AssertionError('MultipleInvalid not raised')
... except MultipleInvalid as e:
...   exc = e
>>> str(exc) == "not a valid value"
True
>>> schema({})
{}
>>> schema = Schema(dict)  # do this instead
>>> schema({})
{}
>>> schema({'extra': 1})
{'extra': 1}

```

homeassistant/core.py

@@ -113,7 +113,13 @@ class HomeAssistant(object):
         else:
             self.loop = loop or asyncio.get_event_loop()
 
-        self.executor = ThreadPoolExecutor(max_workers=EXECUTOR_POOL_SIZE)
+        executor_opts = {
+            'max_workers': EXECUTOR_POOL_SIZE
+        }
+        if sys.version_info[:2] >= (3, 6):
+            executor_opts['thread_name_prefix'] = 'SyncWorker'
+
+        self.executor = ThreadPoolExecutor(**executor_opts)
         self.loop.set_default_executor(self.executor)
         self.loop.set_exception_handler(async_loop_exception_handler)
         self._pending_tasks = []