Update erltrek.hrl

* Add type game_state()
Update erltrek_event.erl
* Change timer_tasks/2 to timer_tasks/1 as game_state() type is defined
* Add clear_command_buffer/1
* Change calling methods to erltrek_scan module functions
Update erltrek_game.erl

* Change GameState definition as in game_state() type, Tick value added

* Change GameTimeState to GameStateAndTimer
Update erltrek_scan.erl

* Change lrscan/5, srscan/5 to lrscan/1, srscan/1 to accept game_state()
Update erltrek_setup.erl

* Change setup_state/1 to also initialize Tick value as game_state() definition changed
Update erltrek_move.erl

* Refactor impulse/3 and impulse/5 by splitting into multiple functions