Store block gid and neighbor refinement levels in sparse packs

[brryan]

PR Summary

For certain discrete methods we need to know the refinement level of each cell across a face. This information is not currently available inside compute kernels. This PR add this data to sparse packs, along with the gid of each current block in the pack, which is also needed for certain algorithms.

PR Checklist

• Code passes cpplint
• New features are documented.
• Adds a test for any bugs fixed. Adds tests for new features.
• Code is formatted
• 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.
• Docs build
• (@lanl.gov employees) Update copyright on changed files

[brryan]

There's currently no testing for this, I wasn't sure where the best place for unit tests might be. The sparse pack unit test doesn't initialize the necessary data in MeshBlocks, and I wasn't sure how to get MeshBlocks out of the forest machinery in test_forest.cpp

[brryan]

This would obviate #1010

[lroberts36]

This LGTM, but a few comments below about how we might save some space or remove the extra deep copy.

[brryan]

There's currently no testing for this, I wasn't sure where the best place for unit tests might be. The sparse pack unit test doesn't initialize the necessary data in MeshBlocks, and I wasn't sure how to get MeshBlocks out of the forest machinery in test_forest.cpp

Still untested but I did experiment in the fine_advection example that the GID and Level functions I added both don't segfault and return not-obviously-wrong data on both host and device.