Allow interrupts for space ships to trigger only at a planet

[mrvn]

TL;DR

The trains have an interrupt condition "At specified station", add that for space ships too.

What?

Interrupts for spaceships should have a contion "At specified planet" and "Not at specified planet".

Why?

I have a spaceship at Nauvis with 3 interrupts to go to Vulcanus, Fulgora or Gleba to fetch science packs. To travel safely the ship must return to Nauvis to refresh it's ammonition stores and in case of Gleba the contents spoil and need to be delivered quickly. So what I want is for the interrupts to only trigger when the space ship is at Nauvis. It should then go to the targeted planet and return before the next interrupt fires.