Expose body suffixes for surface, water, and children.

[Dunbaratu]

KSP's API has these bits of information about a Body that we aren't exposing to kOS:

Body.ocean - bool - True if the body has a liquid sphere at sea level. False if its dry and "sea level" is just a number.
Body.hasSolidSurface - bool - True if the body has any terrain polygons. False if it's all gas like Jool.
Body.orbitingChildren - List - the children of this body (i..e moons of a planet or planets of a star). Right now you can only walk the tree of bodies upward from child to parent via the :BODY suffix (i.e. ship:body:body is the body the body you orbit orbits). There's no way to walk the tree downward from parent to child. This suffix would provide that.