[Therion] Get shortest route

[Tarquin Wilton-Jones]

> I implemented such functionality (not the visualization) a while ago
> as a little exercise in Python. If you know how to run a Python
> script, then you might find this useful.

Awesome!

I would love for that to be built in to Aven, so it could actually
highlight the route too (you know the problem, you give someone an inch
they ask for a mile).

It's something I have wanted when showing someone a survey in Aven;
"Show me the route I took". That is not always the shortest route, but
much like with Google Maps, it would use the shortest route between
control points.

Instead, I end up manually copying it into an image editor, and adding a
background along the route.

(This is kind of off topic for Therion of course, but actually, I would
love for Loch to have a lot of the features that I still rely on Aven
for, such as selecting stations and splays and measuring between them.
So I guess that would be needed first!)