Update tetrisGame.c

Changes:
-Added piece shadows (also known as ghost pieces: http://tetris.wikia.com/wiki/Ghost_piece). As mentioned in a Notice below, we may change the shadow's tile pattern but the top left pixel of each square of a piece shadow shouldn't be lit. This is because that is where checkOverlap, checkLines, and addGarbage's topOut checker look to determine if a location is occupied. Lighting that square would require significant work and would also slow the program down.

Notices: (*changed from last commit*)
-The pattern for the piece shadows (http://tetris.wikia.com/wiki/Ghost_piece) can be changed from what is used in this version, but it shouldn't use the top left pixel in each of its squares. We may not use piece shadows at all depending on if they improve or hinder readability on the LED screen.
-This version of the code treats a long side of the LED array as the bottom of the screen. This may not be the case for the final single-player version of Tetris, but it makes testing the code easier.
-This version of the code includes a global 3D array to temporarily skirt the development complications of a planned tetrominoes.h, which would just include that 3D array.
-This version of the code includes a placeholder menu. It also includes test input handling for Windows, which can be enabled in Windows by de-commenting everything below the two "/*Windows:*/" tags and commenting everything below the "/*Linux:*/" tags, as well as de-commenting the body of getLeftInput(). The keybindings are as follows:
A - shift left
D - shift right
S - "soft drop" (shift one space downward)
W - "hard drop" (shift all the way downward and spawn a new piece)
Q - spin counter-clockwise
E - spin clockwise

To do:
-Clean up the code in general.
-Consider options for displaying the next piece(s) and the held piece. The code for handling this data would be quite simple to write, but the code to display the information would be dependent on screen size and layout.
-Consider ideas for when to call addGarbage.