Exlcude key frame from buffer underrun check, and increase lowest bitrate in BasicBufferModel. Both changes are needed because of a known issue (#495). Change-Id: If5e994f813d7d5ae870c1a72be404c8f7dbbdf27
Adds some basic datarate control tests.. Change-Id: I6eff18aa58ef7cfd14886c6b1e048247cd1ad247