GabbleRosterItemEdit: allow removal from all other groups
GabbleRosterItemEdit: allow removal from all other groups

This is necessary to implement SetContactGroups().

jku/telepathy-gabble,Ziemin/telepathy-gabble,Ziemin/telepathy-gabble,mlundblad/telepathy-gabble,Ziemin/telepathy-gabble,mlundblad/telepathy-gabble,mlundblad/telepathy-gabble,jku/telepathy-gabble,Ziemin/telepathy-gabble,jku/telepathy-gabble