CCFileUtilsApple: Change getWritablePath() to return Application Support Directory subdir

This is a design decision, but the Application Support directory seems more appropriate for writing UserDefaults, etc. This follows the directories used on Windows (Local Settings dir), Linux (~/.config), and Android (/data/data...).

This commit returns a directory under Application Support using the Bundle ID. This path always writable in both sandboxed and non-sandbox OS X apps and on iOS.

See Apple's [File System Programming Guide](https://developer.apple.com/library/ios/documentation/FileManagement/Conceptual/FileSystemProgrammingGuide/AccessingFilesandDirectories/AccessingFilesandDirectories.html#//apple_ref/doc/uid/TP40010672-CH3-SW3)