Extract board outline

[pingswept]

When pcbmode is run with the -e flag now, it extracts the location of the routed paths, vias, documentation, and components, but not the board outline (or the PCB color legend). This means that any adjustments to the outline are lost in the normal compile-extract-compile workflow, or they have to be redone on every cycle.

[saardrimer]

I'm starting to work on the next version of PCBmode at branch cinco-master.

I plan on adding a specific switch for extracting the outline (similarly to --extract-refdefs). I suggest:

--extract-outline