iOS 7 adaptations

My attempt at an iOS 7 adaptation. Instead of trying to make the blur work I went for a white background and black text.

The spinner uses FFCircularProgressView (https://github.com/elbryan/FFCircularProgressView by @elbryan).

The method used is called ``+iOS7StartSpinInView:(UIView *) view WithDownload:(BOOL)download`` where download switches the downward-pointing arrow in the progress view on and off. The actual progress view is also exposed using a ``@property`` and thereby progress can be set and it will switch from an indefinite spinner to a definite one to a checkmark automatically.