issue #358 - DEVELOPMENT: Implement Start/Stop/Pause stream for video
files 
http://agalaldev.info/dev/mantis/view.php?id=358

- Implemented pause on all levels
- startStream call is now synchronous on the SourceManager level, and we
wait till a valid frame is available to continue with startStream series
- end of stream is signaled whenever the VideoSource detects end of
stream, it is signaled on two levels:
-- VideoSource to SourceManager
-- SourceManager to Session

- Updated launch tabs, such that filters tab is contributed by the
filters plugin instead of video general plugin
-