Tooltips for blue/green rings

[darksidelemm]

We've had some questions as to what these rings represent, so perhaps we should have a hover-over tooltip.

Blue ring: Line-of-right (radio) horizon of the payload. Green ring: Payload is greater than 5 degrees above the horizon within this circle, which indicates it should be fairly easily receivable.

[smwnwrght]

I hadn't realised that! It may be easier to just add this info to the user guide.

[TheSkorm]

Putting it on the edge of the circle is a little annoying. For now I've placed it on the "title" (where the km is listed) which is probably good enough?

[TheSkorm]

In https://testing.v2.sondehub.org