Added / operator for vector, double.
Added Truncate method to Vector2.
Adventurer.Update now implemented.

Keyboard.IsKeyDown() throws exceptions now because it is called from another
thread.
temp
Added Keyboard class.
KeyboardSteering now works without exceptions.
Adventurer now takes a force parameter in its constructor.
Removed an unnecesary time update which caused the elapsed time to always be
0.0.
Vector2.Truncate now returns the new value.
_timeSinceLastUpdate in GameForm now gets updated again.
GameForm.GameLoop() now has a Thread.Sleep(1) to prevent the game from going
too fast.
Inverted Up/Down keys in KeyboardSteering.
Gave Adventurer better values (force/speed etc)