Shortening Ifs and Implementing K.O state "restart"

- Shortening Ifs on the character’s “move()” method
- Moving pause/unpause actions to “playing”/“paused” gamestates only.
- Implementing ability to rester the game on “gameOver” state
"Vanish Skill" responsibilities rearranged

- The skill is responsible to know who it is and tell the gameLoop this
info
- The gameLoop gas a list of all skills on the field, and is
responsible of adding/removing skills from it.