edge: use more SDP helpers in peerconnection shim
edge: use more SDP helpers in peerconnection shim

jan-ivar/adapter,Acidburn0zzz/adapter,Acidburn0zzz/adapter,xdumaine/adapter,Acidburn0zzz/adapter,jan-ivar/adapter,webrtc/adapter,xdumaine/adapter,webrtc/adapter