JumpTime, Iterations/frame, units

Finalized units--including time which is now displayed in days.
Changed jumpTime method to be more accurate with orbitals
Changed fast forward to iterations/frame
Encapsulated gravity calculations into one method
I will add comments etc. to make this more clear.

Essentially, JumpTime takes days since the user sees days displayed in the app and needs to be able to enter days. The function then converts the days into hours so that it knows how many times to run the GravityMotionIteration which takes g_timeValue which is a representation of a fixed number of hours each time.