WIP: Gaussian quadrature

[BenWibking]

PR Summary

This adds Gaussian quadrature with a fixed number of nodes. This is just a Kokkos-ized version of the Boost::math implementation.

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
• CI has been triggered on Darwin for performance regression tests.
• Docs build
• (@lanl.gov employees) Update copyright on changed files

[Yurlungur]

This is cool! But it strikes me as a mighty big hammer, as this implementation is very general.

[BenWibking]

@Yurlungur Can you re-review this PR?

I assume Catch tests are also needed. Let me know what scope of tests would be appropriate for this.

[Yurlungur]

Thanks for addressing all my changes! Yeah, some catch2 tests would be good. Maybe integration of a polynomial of the correct order, and showing that the gauss quadratrue gets it exactly on both host and device would be good? e.g., if you use 7th order gauss quadrature, you should be able to integrate a 6th(? might be getting the appropriate order wrong) order polynomial exactly.