Created GetStream, a function used to get the stream descriptor for a
single stream. This allows for finer control over the stream compared
to the batch GetStreams.
Added "trick_play_factor" to GetStream so that the trick play factor
did not have to be added the stream descriptor value and "injected"
into the stream.
Change-Id: Ifbde64b961a673aafa5f6d21f33a68d02fb46610