MacGui: Live Preview Initial Implementation

MacGui: Live Preview Initial Implementation
- Uses a separate instance of libhb called fPreviewLibhb to do the preview encode. Bypasses the queueing system so you can encode a live preview on one source while encoding another.
- All facets of the encode are replicated (including but not limited to audio tracks, subtitles and picture filters) *except* 2 pass. For speed's sake we only do one pass which should be more than sufficient for a 6 to 60 second preview.
- Live Preview clips are stored in "~/Library/Application Support/HandBrake/Previews/" and remain until a new preview is called for of the same format in which case the old version of "mymovie.mkv" would be replaced with a current version called "mymovie.mkv".
- Uses QTMovieView and QTMovieKit to show 5 - 60 seconds in 5 second increments  (determined by a user set NSPopUpButton) of a live preview from the starting point of any of the existing 10 still previews.
- Preview window is now non-modal so can be kept open to see the effect of changing presets, etc.
- Next and Previous buttons replaced with a 10 position slider
- Live Preview is shown same as users QuickTime implementation would show it. ie. without Perian installed, mkv's will not play back, etc.
- Uses QT's stock controller bar with volume, scrubber and single frame advance buttons.
- Known Issues: Movie alignment against the still preview considering the additional height of the movie controller bar. Particularly using loose anamorphic. I am sure there are others.

git-svn-id: svn://localhost/HandBrake/trunk@1951 b64f7644-9d1e-0410-96f1-a4d463321fa5