Systeminfo tweaks

This PR adds two little tweaks for the SystemInfoView:

1. Ever needed to go to a C or D component of a ternary/quadruple system and on arrival noticed that it would be a travel of hundreds of AUs and you wouldn't meet a mission deadline? The required information to plan ahead for such cases currently isn't available. The first commit adds the required information of the orbit of the (A,B)-component and C or (C,D)-component around their common gravpoint.

2. Altitude information is only available when close to a body (e.g. in its atmosphere). To start breaking you often need to know it in advance. The second commit adds the body radius in kilometers additionally to Earth/Sol radii.