Sensors should be available through the API

[rarroyo6]

Some of the sensors, such as "Battery" are available through MQTT but not through the HTTP state API. All the sensors should be available through both interfaces, since on some installations, MQTT is not running because it's not being used for anything else.

[GernotAlthammer]

The sensors (e .g. "battery level" in %) of my Galaxy Tab A7 are available through the HA "Mobile App" where the tablet is also listed as device.

[billchurch]

See #341