Add option to generate arbitrary rectangular (prism) regions.

[RyanWollaeger]

Background

• It can be useful to delineate regions for an X3D mesh, where each region can have different properties ascribed to it.

Purpose of Pull Request

• Add ability to specify any number of rectangular (prism) regions with arbitrary matids (called reg_ids on command line).
• For the changeset here, the matid field in the main X3D file is consistent with the region file cell partitioning (but the region file enumeration - Reg1, Reg2, etc - is not equal to the matid value per region).

Description of changes

• Add optional list inputs for region id and region bounds:
  • --reg_ids is a list of matids per region,
  • --reg_bnd_per_dim is a serialized list of boundaries dimensions, similar to --bnd_per_dim but for each value in --reg_ids (in the same order).
• Sanity check region list sizes if they have been specified.
• Calculate a basic cell center and check if it is in the region.
• Use region ids for matid field and create region file output.
• Default to one universal region (matid=0) if regions unspecified.
• Add example to README.md.

Status

• Reference:
  • Pre-Merge Code Review
  • CDash Status
• Checks
  • [x] Travis/Appveyor CI checks pass
  • [x] Code coverage does not decrease
  • [x] Valgrind test passes
  • [x] Toss3 checks pass
  • [x] Trinitite checks pass
  • [x] Code reviewed/approved, sufficient DbC checks, testing, documentation

[codecov[bot]]

Codecov Report

Merging #1114 (9e90c03) into develop (385284a) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##           develop   #1114   +/-   ##
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  Coverage     88.9%   88.9%           
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  Files          373     373           
  Lines        19570   19570           
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  Hits         17416   17416           
  Misses        2154    2154           

[RyanWollaeger]

It appears one coverage check is not passing. Going to try rebasing this PR against develop to see if it is avoidable.

[KineticTheory]

It appears one coverage check is not passing. Going to try rebasing this PR against develop to see if it is avoidable.

Don't bother with the rebase. The coverage is still good. If this is ready, let's just merge it.

[RyanWollaeger]

It appears one coverage check is not passing. Going to try rebasing this PR against develop to see if it is avoidable.

Don't bother with the rebase. The coverage is still good. If this is ready, let's just merge it.

Sorry - missed your comment and just rebased (doesn't hurt I suppose).

[brryan]

LGTM