add MUC utility functions to gabbletest.py
add MUC utility functions to gabbletest.py

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