add raw dash audio source widevine support

Kai DeLorenzorequested to merge
raw-dash-audio-widevine into master

This is needed for Spotify. There are a number of tracks ~30% that don't contain correct pssh information (they contain PlayReady info instead of Widevine info). The work around is to create a DASH manifest with the correct pssh.

Edited by Kai DeLorenzo

Merge request reports