UserWorkBeforeRestartOutput

[brryan]

PR Summary

We have a downstream need to call a third party library's restart capability when writing our own restarts. This PR adds hooks for Mesh and MeshBlock analogs of UserWorkBeforeOutput that are only triggered during restart outputs.

PR Checklist

• [x] Code passes cpplint
• [x] New features are documented.
• [ ] Adds a test for any bugs fixed. Adds tests for new features.
• [x] Code is formatted
• [x] Changes are summarized in CHANGELOG.md
• [ ] Change is breaking (API, behavior, ...)
  • [ ] Change is additionally added to CHANGELOG.md in the breaking section
  • [ ] PR is marked as breaking
  • [ ] Short summary API changes at the top of the PR (plus optionally with an automated update/fix script)
• [ ] CI has been triggered on Darwin for performance regression tests.
• [x] Docs build
• [x] (@lanl.gov employees) Update copyright on changed files

[Yurlungur]

@brryan is this ready for review? It's still marked WIP

[brryan]

@brryan is this ready for review? It's still marked WIP

@Yurlungur Yes it works but I just wanted to see what people think about including OutputParameters* in the function signature for UserWorkBeforeRestartOutput (and somehow extending UserWorkBeforeOutput in the same way?) so we could get things like output filename downstream.

[brryan]

OK I updated this to reintroduce explicitness around nullptr with std::function and I removed the per-MeshBlock version of UserWorkBeforeRestartOutput. What I did not do is:

• Remove the per-MeshBlock version of UserWorkBeforeOutput

• Change the signature of UserWorkBeforeOutput to include OutputParameters.

  That would pick up two breaking changes so maybe we want to get some consensus on a separate PR that refactors some of these hooks sometime in the future? If so I think this is ready to go, @pgrete if you are OK to approve (and others don't want to pause before merge) I will then go ahead and merge this in.