Maneuvers, state changes about satellitetoolbox.jl

[ronisbr]

Hi @ageofabenius

In fact, this is a long standing feature I need to implement. In this case, we need a numerical propagator in which you provide the additional forces to be applied. The code is written, but it need much more testing. For impulsive maneuver, it should be "easy" to just reinitialize a new propagator with the mean orbit elements after the impulse. For drag maneuvers, then it will be difficult, I think.