on-screen, and I can drag the label. That's progress. Also
implement a bunch of untested expression stuff, since I'll need
that for the values of the dimensions, for example.
[git-p4: depot-paths = "//depot/solvespace/": change = 1668]
the plane basis vectors) work, easy. Tweak the text window a bit,
for cosmetics, and start to add the symbolic expression code.
[git-p4: depot-paths = "//depot/solvespace/": change = 1667]
