Changed inventory look, buttons, and MenuItem.cs

Changed how the inventory looks.
Changed how MenuItem.cs takes its drawbox
   Now accepts "percent points" of the total screen realastate for
   it's drawbos. This allows for proper scaling.
Changed the coordinates of the main menu button to accomodate the new
percent points system.
Menu.cs now takes two paramaters: The current screen x and y coordinates
of the screen you want it to scale to.