Bugfixes, including one for seeking backwards not working correctly.

1. Deleted classes that were unused and/or unnecessary.  
2. Fix for seek on startup that was due to copy/paste from the HDS codebase
3. Fix 1009 null reference crash
4. Fix issue where multi-bitrate streams would load the wrong file initially making startup time a bit slower.
5. Fix seeking backwards bug--the enhanced seeking codepath needed to account for backwards seeks in its logic.