Group thermostats #8

Most (if not all?) hub-based thermostat systems allow you to group thermostats by e.g. room and set temperatures and schedules for a whole room at once, instead of doing it for every thermostat in turn.

Being able to create groups, attach thermostats to groups, set values on all thermostats in a group, and read/write from/to a whole group at once would be awesome.

(Having an implicit all group which you can use to set e.g. vacation for all thermostats in your home at once would also be great.)