Add operation_mode and action for Niko Switches

[sjorge]

Merge after Koenkk/zigbee-herdsman#515

[sjorge]

It took some trial and error to get this all to work, the switches only send the action when in decoupled mode.
Sadly they cannot be bound to a different device or group, so it's only usable for automation in say HA or node-red.

I only still have access to the single variant, but someone with the double variant was able to confirm they could decouple it using the write convertor (this is great for debugging and testing btw! <3)

As far as I can tell the double variant just has a second endpoint that duplicates everything from endpoint 1.

[sjorge]

The omission of value 0 for the tz converter for the opperationMode attribute is intentional, the device nicely spits out an INVALID error when writing unsupported value, however if you write 0, the device soft-bricks and needs to be removed from power and then rejoined. It seemed best to not allow writes of anything not in the set of known values.

[Koenkk]

Thanks as always 👍