Use just one function to add elements to pipeline
Use just one function to add elements to pipeline

This way it will be easier to modify automuxerbin to use other elements
like encodebin.

Change-Id: I1f58efa4b00c881da87307b632a9bfd52015592d

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