MacGui: Initial x264 presets implementation.
- Note: HB Built-ins are not updated as needs more testing
- Backwards compatible afaik for older presets including custom.
- Queue Item editing function needs to be updated yet.
- Preset import/ export will probably need work as well especially since some kvp's seem to still be up in the air.

git-svn-id: svn://svn.handbrake.fr/HandBrake/trunk@5126 b64f7644-9d1e-0410-96f1-a4d463321fa5