Remove need for "execute" state to receive constructor args

[Frimkron]

The default state generator, execute must be declared with the same arguments that should be passed into the constructor. It would be less "magic" to let the user declare an actual __init__ method with the arguments and not require arguments for the generator.

A downside to this is that the user would have to remember to invoke Entity.__init__ or else the entity setup wouldn't complete properly. A possible way of ironing out this might be to move the entity setup to the __new__ method instead although a) this might be just as "magic" and b) it might just be moving the problem