V023.01

-Implemented a method CanFall in leven and map class.
-Implemented a method Fall in player class.
-Starting to work on gravity and array of collisions (still not
finished).
-Added comments on code and a bit of refactoring.-Corrected bug in
MapIntro constructor and Map constructor.
-Gravity almost work, but it need some correction anyway.
-My player falls now, but it need some correction anyway.