goodifying UI

- added 3 placeholder courts for stage select
- refactored menus to be on more of a grid system
- refactored scene loading to be based on scene name rather than load order
- re-scaled menus to work better across display sizes 
- added visual assets to character and stage select screens
- shuffled and reorganized GUI asset file structure
- tweaked score display on game screen
- added countdown clock and point scored messages to game screen