Updates to Player and Enemy shooting/pathfinding

* Player can shoot enemies with currently selected weapon via LMB

* Enemies shoot when in range of Player
- Player cannot move while any enemy bullets are active

* Basic level-up mechanic implemented

* Work on enemy pathfinding started
- Player's last set of moves are added to a DS_List
- If Player was never in Enemy's range, enemy should move randomly
- If Player was in Enemy's range but left, Player's moves that are still
in sight range of enemy should gain additional weight

* Collision detection with Player and collided fog tiles improved
- TODO: figure out how to add player's moves diagonally without
disturbing nearby tiles