Bom weather platform (#5153)

* Fix typo

* Auto-config for `sensor.bom`

Deprecate (but still support) the old two-part station ID, and move to a
single `station` identifier.  Any combination of these, including none,
is valid; most results in downloading and caching the station map to
work out any missing info.

* Add `weather.bom` platform

Very similar to `sensor.bom`, but supporting the lovely new `weather`
component interface.  Easier to configure, and does not support the
deprecated config options.

* Review improvements to BOM weather

Largely around better input validation.

homeassistant/components/weather/demo.py

@@ -79,7 +79,7 @@ class DemoWeather(WeatherEntity):
 
     @property
     def pressure(self):
-        """Return the wind speed."""
+        """Return the pressure."""
         return self._pressure
 
     @property