edit (again) they should be on 2.3.0 Stable
see: Design Pattern: Working with Groups in Rules - #70 by Nicholas_Waterton
and: Rules | openHAB
This: Allow binding DSL Rules to all items contained in a group by jmsjones · Pull Request #4800 · eclipse-archived/smarthome · GitHub was merged on Jan/18 and OH2.3 stable was released on May/18, so it should be there