lint on solid_geometry, created volume_1
More changes...
Added a "sketch" to graphie-3d  for 3d line drawings.
Start +- Rat Expr 6
Add questions with trailing zeros
Remove irrelavant file
Have some exercises where decimals are equal but one has a trailing 0
Reduce frequency of trival equals questions
Make comparing decimals 2 questions more interesting
Add more confusing questions with 0s to comparing decimals 2
Ensure numbers are not 0
Added units to the answers, changed out \Box for "?", added a 3D figure to box-minus-box, and made a few numbers latex which were not.
Added an problem with a fixed box to count the cubes of (to practice 3d imagination).  Also added a "weird shape" problem which generates a random shape with between 3 and 7 cubes.
Fix bug caused by treating term as an expression
Fix issue with negative signs and avoid additional cancelling
Improve how trailing zeros are dealt with
Updated graphie-3d to use the painters algorithm.  Added a few more problem types to volume 1.
added some more options to graphie-3d, weird shape now looks snazzier.
Merge pull request #59043 from petercollingridge/multi-rat-exp-4

Fix bug caused by treating term as an expression
Merge pull request #59065 from petercollingridge/sim-rat-exp-4

Fix issue with negative signs and avoid additional cancelling