added-enums-for-directions-and-method-stub-for-get-node-by-direction
changed to protected for direction enums
Fixed simple board to be cartesian
Added tests for simple board
Merge branch 'add-todo-get-node-by-direction' into SimpleBoard

Conflicts:
	src/kth/game/othello/simple/SimpleBoard.java
Implemented nextNodeInDirection & more
Added tests for immutability and node out of bound