added Range & Level
store variables in Physics instead of speciffic engine
added Persistent object

- score encode/decode
dynamic Obstacle Velocity
added Falling objects
fixed bounce collision

- use max instead of random since it can be smaller
moved level out of Physics

- moved score into Level
using multipple Levels
added Falling collectables

- without collision
added gravity and collison for Collectables
added Player animation and sliding
added run.rkt
changed Object system

- use define instead of kClass symbol
- don't wrap getters in a function
collectables with Image animation
serialize and persist Levels
improved Menu
fixed bug in menu + correctly persisting level

- menu needs a procedure to *not* draw "new highscore"
- persisting needs to happen when the menu is shown, not when a new game
  starts
- Makefile clean, resets level data
Merge branch 'refactor'