MacGui: Preset Import / Export initial implementation and auto updating of built...

MacGui: Preset Import / Export initial implementation and auto updating of built in presets.
- Preset Import / Export:
-- Export is only available to custom user presets.
-- Export is only the selected preset at this time.
-- Exported presets will be tagged with their build number.
-- Import of mutiple presets.
--- Compatible with LinGui presets.
--- NOT compatible with WinGui presets at this time.
- Built-In preset auto-updating:
-- Adds the key/value pair to the UserPresets.plist file for key "PresetBuildNumber".
-- If the HandBrake.app build number as defined in the Info.plist key "CFBundleVersion" is > the built in presets  "PresetBuildNumber" then the - (IBAction)addFactoryPresets:(id)sender is called to automagically update the built in presets.
-- An alert window is shown along with a system beep ( can be turned off in Preferences -> Advanced for svn mavens and devs) to tell the user that the built in presets are going to be updated.
-- NOTE: First launch of this build will initiate a built in preset update even though the built in presets are the same, since the build number will be added to the built in presets.

git-svn-id: svn://localhost/HandBrake/trunk@2405 b64f7644-9d1e-0410-96f1-a4d463321fa5