Added classes and various changes

- Removed reference to Timer in AuthorizationShellExample comments.
- Removed reference to SelfTest in CertTools.
- NSUserNotificationCenter: Changed event name to more descriptive ShouldPresentNotificationInForeground.
- Added Cocoa.NSSound class.
- Added NSSoundExample window.
- Added Cocoa.AVAsset.
- Added Cocoa.AVAssetTrack.
- Added Cocoa.AVMetadataItem.
- Added new classes to Cocoa.NSObjectFromNSPtr.
- Replaced For Each in Cocoa.NSObjectFromNSPtr since order matters.
- Version 174.