Operators for point type.
Add cubic millimeter
Add note for meshing.
Simulation work.

Model creation is working. Volume calculation (which involves meshing)
it very slow - probably best if this is necessary to batch these
operations or adjust meshing parameters to acceptable limits.

Corrections (and requisite tests) to path generation which did not
correctly start at the start position.

Added simulate_path test as initial integration test before modifying
main Machine object.