Basic UIImageView Support

Allows for the loading of image resources dynamically through an NUI
stylesheet for a UIImageView.
Merge branch 'dev' into ImageView
Created NUI ImageView Category

Implemented UIImageView+NUI category.
Forgot to add swizzle method (again!)

Fixed crash, and finalised barebones UIImageView support, by adding in
the swizzleDidMoveToWindow method for the UIImageView class.