Impose compatbility of mesh and space group (pspc and pspg).

[dmorse]

Create a function in SpaceGroup that takes the dimensions of a mesh as an argument, and checks if all symmetry operations in the group maps the mesh onto itself (all mesh nodes must be transformed to positions that also lie on mesh nodes). This requires that

• If a group contains translations by a fraction N/D in direction i, the number N of grid points in direction i must be an integer multiple of D, so that NM/D is an integer
• If there exists and operation that maps direction i into direction j, the number of grid points in directions i and j must be equal.

[dmorse]

Completed 7/4/2023, to be incorporated into patch version 1.0.3