0003602: FFDShow Subtitle and Post Process not disposing when close Directshow Graph (1 Viewer)

[MediaPortal-Bot]

Improve the Dispose method when using ffdshow, in actual svn, we didn't dispose FFDShow related ComObjet.
After open many video, memory grow up and can crash MP.

http://mantis.team-mediaportal.com/view.php?id=3602

Open the issue in Mantis...