Implement mediaObjectImpl stub methods

Change-Id: Ie47cddc85bca18ac357c8fb99016e2c320bf36dc
MediaPipelineImpl: Implement stub

Change-Id: I44c8df626910d513568a2df1415e68485b57fcdf
Add creation and serializatio test

Change-Id: I5d407f79b80bbea2b0b76830725ffaa168b8866f