Some more structural changes

Moving as much logic as possible into the init of the pygame
and PIL classes.

The next step is to take out anything duplicated, and move it out of 
these classes and into the main class.
Added image pattern format

Much better than using text files, and allows us to determine the size
and offset automatically instead of specifying it explicitly.

In fact, the offset doesn't have to be specified at all. Yay!