Work on instancing a fighter (Ref #2)

* Set unit fields as protected
* Add constructor for a fighter with initial values
Factories #2

* Modify constructor in ShipFactory interface to specify position
  and rotation.
* Fix ConcreteShipFactory similarly
Factories: ConcreteShip_Fighter #2

* Implement turning
* Implement thrust
Merge pull request #11 from bjorfoss/iss3-factories

Iss3 factories