Make time-to-next-maneuver more convenient to set up

[lpgagnon]

Problem: after setting up a flight plan with a few coasts and maneuvers, I want to set up one more maneuver at a particular Pe node.

Hovering the Pe node gives me an amount of time from "now". But to figure out how long a coast that should translate to, I have to first calculate how long after "now" the previous maneuver ends at by adding up coasts and burn times. Not a big problem, but inconvenient, and seems like something that can be improved in various ways.

Options I see:

• where the coast-between-maneuver time is shown, also show cumulative time since start of plan (or possibly the delta between "now" and the following maneuver)
• allow entering time of maneuver as an offset from start of plan instead of from previous maneuver
• allow picking a time by clicking a node (fancier, a more convenient fix for this specific case but maybe doesn't help with other cases)

[pleroy]

I am implementing the second option.