* KEF: add support for play, pause, next track, and previous track
* bump aiokef to 0.2.7
* run isort
* do not dynamically change the supported features
* add KEF speakers platform for the integration
This will work with the KEF LS50 Wireless and KEF LSX speakers.
The development of this code happened on https://github.com/basnijholt/media_player.kef
* rename DATA_KEF -> DOMAIN
* use aiokef v0.2.0 and support LSX and new features
* sort imports
* fix @MartinHjelmare's suggestions
* remove _CONFIGURING
* change STATE_UNKNOWN to None
* use lat and long for unique_id
* bump aiokef to v0.2.2
* use config[ATTR] instead of config.get(ATTR)
* use getmac
* fix case when MAC is None
* use host as instance lifetime id
* fix requirements
Bas Nijholt