Resizing sort of works in BattleScreen

Does not correct map mouse though. It does not stretch the textures
which is what we want.
Also now uses a instance variable for the how large a tile is in the
screen.
Resizing sort of works in WorldScreen.

Same problem and functionality as the resizing in BattleScreen.
Also now uses an instance variable to keep track of the size of a tile
in the screen.