#266 *marknotintersection in HyperMesh tcl

*marknotintersection determines the intersection between two marks and stores everything but the intersection in the first mark in HyperMesh tcl.

To delete the elements not shared by marks 1 and 2:

*createmark elems 1 1 2 3 4
*createmark elems 2 4 5 6 7
*marknotintersection elems 1 elems 2
*deletemark elems 1

This will delete elements 1, 2, 3, 5, 6, and 7.