Time scaling factor

[ghost]

Sometimes I want to simulate a rather long mission, with some interesting happening in the middle of the flight. PX4 simulation has a PX4_SIM_SPEED_FACTOR that can be set to speed up or slow down the simulation. It would be great to have this implemented too. As far as I know this is set at the start and can't be changed during runtime, but it would be even more useful if we could fast forward during flight and then at the interesting part slow it down sub factor 1 for example.