Removed custom audio parsing code for MEDIASUBTYPE_PCM

This was required only for direct source -> audio renderer connections
Remove DVBSub3.ax related code from BDReader.ax and BDPlayer.cs

TODO: provide a way to change subtitle stream with the native libbluray subtitle support
Remove Blu-ray subtitle support from DVBSub3.ax
Fixed playback position getting reset on clip boundary with seamless branching Blu-rays
Code cleanup in Clip, Playlist and PlaylistManager classes