Gstreamer AppSource Implementation for AV playback on the desktop (#36)

* extract video pipeline into separate method, run go fmt

* added an example of a failure

* use a waveparser, works with an oggmux, just not hearing anything with an audiosink

* added vorbis hack, and now it works

* added queues to the video pipeline

* works

* use vtdec to bring down cpu usage

* add comments

* add fix for NSThread mainloop problem

* minor clean ups, add mac os only compile flag

* minor clean ups, add mac os only compile flag

* add linux adapter

* set sync to false for faster playback

* minor fixes