kmselement: Add audio and video properties
kmselement: Add audio and video properties

Change-Id: I0e1149198dbf9d550557e7d77acc198e7203a9dc

TribeMedia/kms-core,ESTOS/kms-core,shelsonjava/kms-core,ESTOS/kms-core,TribeMedia/kms-core,TribeMedia/kms-core,shelsonjava/kms-core,Kurento/kms-core,Kurento/kms-core,shelsonjava/kms-core,ESTOS/kms-core,Kurento/kms-core,shelsonjava/kms-core,TribeMedia/kms-core,Kurento/kms-core,ESTOS/kms-core