Cleanup internally created group in fix gcmc

[sjplimp]

Summary

Add code in destructor to delete the exclusion group created by fix gcmc. Also the rotation group. Ditto for fix widom.

Related Issue(s)

N/A

Author(s)

Steve

Licensing

By submitting this pull request, I agree, that my contribution will be included in LAMMPS and redistributed under either the GNU General Public License version 2 (GPL v2) or the GNU Lesser General Public License version 2.1 (LGPL v2.1).

Backward Compatibility

N/A

Implementation Notes

Post Submission Checklist

• The feature or features in this pull request is complete
• Licensing information is complete
• Corresponding author information is complete
• The source code follows the LAMMPS formatting guidelines
• Suitable new documentation files and/or updates to the existing docs are included
• The added/updated documentation is integrated and tested with the documentation build system
• The feature has been verified to work with the conventional build system
• The feature has been verified to work with the CMake based build system
• Suitable tests have been added to the unittest tree.
• A package specific README file has been included or updated
• One or more example input decks are included

Further Information, Files, and Links

[sjplimp]

@akohlmey Realized this did not require a new method in group.cpp b/c the group has a custom name - it is not the group specified in the fix gcmc input script command - and thus not checked for by the Group class delete operation.

[evoyiatzis]

@sjplimp fix widom is heavily based on fix gcmc. It worths checking if this modification should be propagated to fix widom as well.

[sjplimp]

@evoyiatzis good catch - I added the same logic to fix widom