Overhauled for improvements and compliance with two-player version

- Optimized some elements -- particularly, placeFood().
- Resolved a bug with initial snake placement.
- Overhauled organization to comply with the two-player version and be clearer. Functions are now split into throwaway test functions, game-agnostic functions (many of which require lodev support), and board-ready functions. The global variables are now local. The snake-collapsing visualization is not present when this code is run in a single-threaded environment, but will display with the intended output method of the LED board.