Game screens

All of the GameOverScreen was implemented. It hasn't been tested, as there were no player objects available in the scene. Additionally, the objects are still not colliding with the AI, despite the alleged fix. The health script has been modified such that when currentHealth == 0, another check will be made if the character is a bot; at which point, it will send a message to the gameovermanager. The GameOverManager has two documented methods. One will change the game to a gameover state. The other will add functionality to the buttons in the gameover menu. Note that each button and the game over menu (the canvas components) now have implementation. Again, this was not fully tested, but note that there are no compiler errors.