Add functions to import and draw paths from an SVG.

[rwb27]

This adds a few utility functions that can load a path from an SVG file and draw them on a box. I have tested only two files, which worked - I'll attach the OFM logo here.

I have also attempted to make a more neutral SVG in Inkscape and in OpenSCAD - but unfortunately neither worked properly. I think that means these functions are unlikely to be very useful without further testing. Nonetheless I'll leave them here in case it's of use to anyone.

[rwb27]

Here are some example SVG files I've used that work.
logo_emblem
shelf_cutout
footprint
footprint_cable_tidies

[rwb27]

Here are some examples that failed.
openscad_smiley
smiley

[MartinScharrer]

Here are some examples that failed. openscad_smiley smiley

Hi, they fail how? The resulting image is incorrect?

I did some similar code in my fork this week (to draw a logo and special cutouts imported from SVG) and I noticed that having multiple z commands in the path does not work, i.e. generates an incorrect image. You need to close the path so far every time a z or Z command is encountered. This should fix the issue.

I added this indirectly by calling ctx.stroke on Z but calling a close-path command might be better. Feel free to compare my code at https://github.com/MartinScharrer/boxes/blob/51598cef72447fa54ddd7c31ee17fd74fa8bed4d/boxes/generators/queentransportbox.py#L121

[MartinScharrer]

The issue #847 might be relevant here. Maybe this is the reason some SVGs fail to render properly. Curves can then changed to edge polylines!

I fixed it as PR #848.