Entity registry (#11979)

* Entity#unique_id defaults to None

* Initial commit entity registry

* Clean up unique_id property

* Lint

* Add tests to entity component

* Lint

* Restore some unique ids

* Spelling

* Remove use of IP address for unique ID

* Add tests

* Add tests

* Fix tests

* Add some docs

* Add one more test

* Fix new test…

homeassistant/components/sensor/blink.py

@@ -61,11 +61,6 @@ class BlinkSensor(Entity):
         """Return the camera's current state."""
         return self._state
 
-    @property
-    def unique_id(self):
-        """Return the unique camera sensor identifier."""
-        return "sensor_{}_{}".format(self._name, self.index)
-
     @property
     def unit_of_measurement(self):
         """Return the unit of measurement."""