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

Change-Id: I0daba2e9eef60d03fca50ca557ea01fdbba5c140

ESTOS/kms-core,KurentoLegacy/gst-kurento-plugins,KurentoLegacy/gst-kurento-plugins,TribeMedia/kms-core,KurentoLegacy/gst-kurento-plugins,ESTOS/kms-core,shelsonjava/kms-core,Kurento/kms-core,ESTOS/kms-core,Kurento/kms-core,KurentoLegacy/gst-kurento-plugins,shelsonjava/kms-core,shelsonjava/kms-core,shelsonjava/kms-core,Kurento/kms-core,Kurento/kms-core,ESTOS/kms-core,TribeMedia/kms-core,TribeMedia/kms-core,TribeMedia/kms-core