Fixed problems with different imports - IOError(cannot identify image file) 

Hi,

sorry to further bother you with this import issue, but I think I found a solution that allows for both ways of import ("import Image" and "from PIL import Image").

It is achieved by extracting the (mutable) registry state to a separate package private module which is imported only from Image.py. Like this we can control the way of import for that module, and we are sure it is not ambiguous. 

If you think it's nonsense or find any issues with it, I just apologize for bothering you.. :)

Best,
Thomas