Provider network MEF UNI EVC update

Added stubs for metro ethernet forum ( #MEF ) user network interfaces ( #UNI ) and ethernet virtual connections ( #EVC ) management support in #bridge module. This will enable MEF recognized attributes to be configured on #PB and #PBB networks.

#Ethernet update 21 ...
[commit e31a4a328e953abfb63a7af6b173878049ccf14c]