Implement pad added/removed callback
Implement pad added/removed callback

Change-Id: I7bb4d0e71e0b6b222afc6b73528464eb461e2d9e

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