More powerful channel selectors

[Yoric]

I'd like to write a Thinkerbell rule (or, really, any send operation) that turns off all lights in the living room. Let's assume that lights are defined by channels with kinds OnOff and Luminosity.

How can I do it?

1. Sending Off to all channels that support OnOff in the living room can turn off devices that are not lights, so this is not what we want.
2. Requesting the list of services that have channels OnOff and Luminosity, then taking the OnOff channels of such services gives us that list, but we need to rely upon the Id of services, which means that the rule will break when we replace the device.

We need better selectors.