mainmixer: Create agnosticbin elements for each port
mainmixer: Create agnosticbin elements for each port

Change-Id: I0daba2e9eef60d03fca50ca557ea01fdbba5c140

TribeMedia/kms-elements,TribeMedia/kms-elements,shelsonjava/kms-elements,shelsonjava/kms-elements,Kurento/kms-elements,TribeMedia/kms-elements,Kurento/kms-elements,shelsonjava/kms-elements,Kurento/kms-elements