Basic physics cleanup to put the scaling back into the named constants

The ship.time_factor value is now available through status, it is the real honest time factor; it is set to 10, because this seems to be the closest to the previous behaviour

Arbitrary constants in time step length, velocity application etc. got removed. Trajectory autoscaling now hopefully works. The engine upgrade now should give an actual engine boost…

Acceleration cap has not been touched. It is easy to tune the basic game physics to work fine without it; trajectory is a problem, though.