The BJ ZLL switches/relays/dimmers are currently exposed as switches
with a non-prefixed endpoint. This causes two issues:

- Dimming is not working for the dimmer modules
- Both `state` and `state_relay` is published as an attribute, where
  only `state_relay` makes sense here. However the Z2M UI and Home
  Assistant auto-discovery were both using the "wrong" attribute.

This commit addresses both issues, but will cause some changes for
existing users:

- Home Assistant auto-discovery will change (device changes from switch
  to light)
- All BJ ZLL devices will have a brightness attribute (and brightness
  slider in the Z2M web UI), even if they do not support dimming. This
  is due to the fact that all devices are reported as the same model
  and Z2M cannot distinguish them.
- The top rocker (endpoint 10) will not be bound to the coordinator
  any more if the module was installed on a relay or dimmer. This is
  just a clean-up, which won't have a practical effect.

We don't need to expose all Busch-Jaeger devices as lights, but only the
ones which are actually connected to a relay or dimmer.

The scenes cluster workaround does not seem to be required for the
battery-powered Busch-Jaeger wall switches.

This will only affect freshly paired devices, existing devices will be
kept es they are.

The switch definition for these devices is actually wrong here, but
let's keep it for compatibility reasons as it has been there first.