Convert radiation problems to cgs

[adamdempsey90]

Background

This removes the special unit systems we had for the two radiation pgens. Now those are just run in cgs units.

Still todo:

• Verify shock problem
• Verify thermalization problem
• Documentation
• Add both problems to our testing

Description of Changes

Checklist

• New features are documented
• Tests added for bug fixes and new features
• (@lanl.gov employees) Update copyright on changed files

[adamdempsey90]

Here is the shock problem with the parameters as set in the input file in inputs/

[adamdempsey90]

@pdmullen can you approve if you're satisfied