Grid Engine Headers

- Have tidied up some of the prototype functions and set by group
- Nothing major, just hopefully lets you get a better feel for how we
pad things out
- Currently working on a level designer that can be used at the command
line - this should be up later today along with some base commands.
Grid_Engine.h --- AGAIN!

— Well, you can never have your prototypes tidied up enough.
— Have clearly demarcated the Tile* BuildGrid() function that creates a
grid that can be accessed across the program.