Advanced Guard Tower fix and improved seen logic

We rewrote the AGT script, so that it now will seize fire immedeatly after the target is out of sight and made it impossible for the AGT to fire directly at it's base like it did before.
Also we changed the seen logic of the AGT and Obelisk to make then charge/fire directly once they can see you. Obelisk walking tactics will be alot harder I expect .