MacGui: Multiple subtitle tracks initial implementation

MacGui: Multiple subtitle tracks initial implementation
- Subtitles now get their own tab
- "None" track is an empty track, add a new subtitle track by switching it to a valid source track.
- First track allows for "Foreign Language Search" which replaces the old "Auto Select".
- Remove a previously selected track by setting it back to "None"
- Sanity Checks:
-- Allow only one Burned In track.
-- Text tracks do not allow burned in to be set.
-- MP4 specific:
--- Allow only one VobSub and force burned in to be set.
---- Trying to set more than one vobsub in mp4 results in a warning, and the first vobsub track is retained.
- Presets: Currently subtitles are not recorded into presets (which they never have been).
- Live Preview:
-- Foreign Language Search is borked for live preview, so is ignored
-- Burned in subtitles work for both mp4 and mkv
-- Text subtitles work for mp4 if set to default (preview has no way to turn soft subs on/off)
-- Text subtitles do not show up in preview window even if checked as default.

git-svn-id: svn://localhost/HandBrake/trunk@2530 b64f7644-9d1e-0410-96f1-a4d463321fa5