Added new tower and enemy.
Weird bug in Screen.updateTower.
Happend after editing constructor of Tower.
When game starts updateTower checks if there are any towers placed(towerMap != null) but it complains that it is null.
Exception is caught but it still fires at the start of game.
Looks like it doesn't do anything to the game but should be repaired.
Added temporary tower attack animation.
I'll add projectiles to towers, which will have attack animations, damages etc.
Added random spawning of enemy types.