iOS 8 fixes

My girlfriend was not happy about the iOS 8 update did break the app, because all her students uses it in all her classes :-)

So here you have a pull request. The most important change was in _Brushes-Info.plist_ where _public.data_ is changed to _public.folder_ to make the app able to save/read data (iOS 8 does not understand _public.data_ for a bundled folder). I also checked _Full Screen at Launch_ in Interface Builder for the _MainWindow.xib_ to make the view work in iOS 8. For some reason it was necessary to import _OpenGLES/ES2/gl.h_ in _WDUtilities.h_ to make it build.

There seems to be a lot of number conversion precision issues when building for 64 bit, but I did just set the compiler to ignore it.

I've tested on an iPad 1 (5.1.1), iPad Air (8.0) and the iOS 7.1 simulator.