File System

Enables read-only access to text files bundled with the application. 

I chose to provide a function exclusively for text like shaders, config files, json, etc. because all of our other file needs will likely require significantly different (and possibly platform-specific) implementations. Textures should be loaded with Core Image on iOS (and maybe libpng on Android), cache files might use an SQL database (or maybe Core Storage on iOS); basically, I concluded that writing a totally general file I/O protocol would be a waste. 

Also: I've converted the OS X platform file to objective-c++ because the Foundation framework makes file I/O really easy (and possibly faster). I see no downside to using objective-c where reasonable.