gmshcall.py to output physical groups if present in .geo specification

[saustinp]

Regarding Exasim/src/Python/Mesh/gmshcall.py:

The current gmshcall function doesn't read in physical groups that are specified in the input .geo file. Physical groups are collections of model entities that are used to alias domains and boundaries, preventing having to manually enter them using logical operations on the coordinate values in the pdeapp script. If the geometry is specified using Gmsh, being able to read in the physical groups from the .geo file will yield significant user time savings in setting up the case.

[exapde]

Thanks for suggesting the idea of using Gmsh physical groups to define domains and boundaries.