Window: show informations about AI, improve UI
TetrisEngine: remove setState as a public method

refactor its uses, replace public interface with tooglePause
BlockPosition: move from tetris.ai package to tetris.generic
AbstractAI: remove movehere method and rewrite the BlockMover

AIExecutor: fix bug that if the AI velocity is set to zero there was a delay for the acceleration to begin
TetrisAITest: fix test for the last modification
move SwingPropertyChangeListener to PropertyListeners