media player: initial implementation

This patch adds API for manage video player.
During player initialization it opens file, initialize video
and audio input, starts audio stream if needed.
Initial player state is paused.
It is up to client unpause player, get first frame and pause again
to get image for preview.
Current player functionality is
- play/pause
- seeking
- mute audio

Change-Id: I8cba50e1ab424d5acde9c38214af2cfe51064607