* add services for DSP
* add homeassistant/components/kef/const.py
* add services.yaml
* fix set_mode
* fix services
* media_player.py fixes
* bump aiokef to 0.2.9
* update requirements_all.txt
* add basic sensor.py
* add DSP settings as attributes
* add message about kef.update_dsp
* remove sensor.py
* fix pylint issues
* update_dsp inside async_added_to_hass
* use {...} instead of dict(...)
* get DSP settings when connecting to HA or once on update
* simplify condition
* do not get mode twice
* remove async_added_to_hass
* use async_register_entity_service
* remove entity_id from schema and prepend _value
* invalidate self._dsp after setting a DSP setting
* schedule update_dsp every hour
* subscribe and unsubscribe on adding and removing to HA
* don't pass hass and set _update_dsp_task_remover to None after removing
Bas Nijholt