Spritesheets, and minor updates

Changelog:

-Added spritesheets for each controller including all primary buttons. Some controllers do not yet have finished sheets, note the missing sl and sr buttons from the sheets.

-Added Xbox 360 Start and Back buttons

-Added Number buttons for the keyboard prompts

-Fixed missing font from initial release

-Minor reorganization

-Planned addition of Controller icons

If you have any suggestions for additions, let me know down below!