Created two-player tetris, rough but fully functional

- Currently, the code is rough and somewhat confusing, particularly in its use of inelegant exceptions in importPiece and other functions. It has full functionality and appears bug-free but needs to be tested more, specifically in regard to garbage lines ending the game and correct piece spawning positions.
- Functions are now split into game-agnostic functions (many of which require lodev support), test functions (to be removed in final versions), and board-ready functions. Functions in the last category are particularly likely to change in the next commits.
- Like all current versions of games, this code is equipped with test input handling using a keyboard on Windows. To use it, de-comment everything below the two "Windows:" tags, comment everything below the "Linux:" tags, and de-comment the bodies of getLeftInput() and getRightInput(). Control of the respective pieces is then linked to WASD and IJKL in theory, but considerations for buffered keyboard input have not been made so only the left piece may be controlled without joysticks(using WASD).