Make ETA:APOASIS return 0 on on hyperbolic trajectories

[ThunderousEcho]

Resolves #2229

[Dunbaratu]

For personal issues I have been away from kOS for a while. I'm coming back into it again and looking at these PRs.

It seems to me that a better solution might be a really big number rather than zero. Not infinity, but something like Single.MaxValue (and the documentation changed to match). I was thinking Double.MaxValue, but because I don't want the chore of proving the code never passes the value through a single float at any point, I think Single.MaxValue would be safer (and still larger than any "real" value an elliptical orbit in the game would return).