Route-planner

[Kroc]

In addition to #32 (combine galactic / local charts), I'd like to put more emphasis on long, multi-jump journeys. To make that viable, the chart should have a route planner that can take a distant target and calculate a route to it. It should have options to favour 'safe' (avoid politically unstable systems) and 'profitable' (favour jumps between high/low industries).

(The code should also be able to do the opposite for missions, e.g. travel a dangerous pirate-ridden route.)

Route-finding is a complex, difficult process so this will take quite some code to pull off. It may very well be that on order to get to one particular system, you have to begin by going the opposite direction. We'll need at least 256 bytes of scratch RAM to mark off what routes have already been tried when dead-ends have been reached. Note that there are often galaxies where pieces of it are completely 'detached' from the rest and if we allow #31 (choose your own seed), almost anything is a possibility!