* Don't set SUPPORT_EFFECT on DemoLight if there are no effects
This requires an update to the group test - previously the other lights
instantiated by the DemoLight component had nothing in ATTR_EFFECT_LIST, but
still had SUPPORT_EFFECT set. This appears to have resulted in the light
group test code setting an effect on the group and expecting it to apply to
all lights, but given that two of the bulbs didn't actually support any
effects (due to the empty ATTR_EFFECT_LIST) this seems like a broken
assumption and updating the test to verify only the bulb that supports
effects has had one applied seems reasonable.
* Add support for exposing light effects via Google Assistant
The LightEffects trait only supports a fixed (and small) list of lighting
effects, but we can expose them via the Modes trait - this requires saying
"Set (foo) effect to (bar)" which is a little clumsy, but at least makes it
possible.
34e2a1825b
