Update GameBoard.java

GameBoard has private variables: 2D tray of Integers; HashMap<Integer(block num), Integer[](block coordinates)> blocks; and Integer[] size (size[0] = numRows, size[1] = numColumns).

GameBoard implements addBlock, taking in a string line from the input file, adding the Integer[] to blocks.

Implements fillTray, filling the tray from the given blocks.

Implements getBlocks, returning the current Board's block set.

Implements empty GameBoard constructor, given x and y dimensions.

Implements new GameBoard constructor, given a HashMap of blocks and size coordinates.