Add create screen

The create screen gui elements are now all present, but not all implemented.  The biggest undertaking was displaying the cryptogram in the preview screen, which can also be used for the solving screen later.

Updating each character when a character is input is currently not working, so this still needs doing.  (ideas?)

Some small changes were made to the cryptogram class as well, as per discussion with Paymahn.

UPDATE 05/30/2013:
Updating letters now works properly.  Rudimentary Check Solution button (prints to console) also implemented.  More changes made to the cryptogram class to support these implementations.