New enemy: The Wall Jumper

Added a new enemy to the game, the wall jumper. This is the fastest of the enemies so far, it also has a special skill, it can jump walls... yes it was pretty obvious. 
This enemy charges its skill by moving, when the skill it's ready it will start searching for paths to the player without caring if there is a wall in between. Once the skill was used it will take some time until is ready again.