Created proper cutting path for leather.

Found out that the export cuts the lowest paths first, so I selected each path
in the cutting order, and moved to top.  Also found that paths can be reversed
with Path > Reverse.
Updated FreeCAD files with measured dimensions.

Obtained leather, rivets, and buttons, and got wood thickness from Peter.
With that, updated lengths.fcstd and notebook.fcstd.  Also found that the
leather is not terribly flexible, but I could imagine it loosening with time.
Leather cutting path with updated dimensions.

Also combined all paths properly as per Peter's instructions, so this should be
ready to cut now.
Created SVGs for all wooden components.

Don't yet know the correct feed speeds, so I haven't made the G-code files.
But I updated the Readme pretending I had, so better do that soon.
Re-did all SVGs to fix scaling issue.

The G-code exporter didn't like that the page size came from FreeCAD with "mm"
on the end.  Originally, I just removed the "mm", but then it interpreted all
sizes in px, which messed up the scaling.  I imported all.svg into a new
document to preserve the right scaling while getting the correct page size.
But then had to re-create all the other SVGs so they would carry the proper
scaling too.
Created G-code for all wood pieces.

According to the thinkhaus wiki, 3/16" plywood floor underlay takes a feed
speed of 300 mm/min.  So these are all ready to cut!
Added license: CC-BY-SA 4.0