Small fixes and convert to ARC

Not much to say. The only thing that should probably be discussed is my adding an extra `@implementation QSController` bit to QSPasteboardController.m to stop the build error on `interfaceController method cannot be found`. Very nasty :(

For opening the preferences - I found a clever solution (to changing from the previously used `NSClassFromString()`...
Open the URL to the preferences with `NSWorkSpace`