#2101: Add Lean_public and Proca thorns to the ET

Comment (by Roland Haas):

I gave this a very quick try on the wheeler login node (so 1 MPI rank only) and it seems to make the test pass. If you want to use it, here's a pull request with that change: https://bitbucket.org/canuda/lean_public/pull-requests/1/npscalar-set-the-absolute-tolerance-to-5e/diff but it really is just copying over Peter's test.ccl from WeylScal4.