WebUI: show a warning for IE < 8.

Things don't look good there for some time now.  IE8+ works fine.
WebUI: Add title with the volume level to the volume grip.
WebUI: Inform the web interface that no audio stream is available.
WebUI: show a "X" when there's no audio available.
Update ZenLib to v0.4.29 r446.
Updated MediaInfoLib to v0.7.68.