Convert reset_internal_energy to C++ and simplify the algorithm

[maximumcats]

PR summary

We now simply evaluate the eint corresponding to small_temp, and reset eint (and eden) as needed to be at least that large. We then apply the dual energy criterion. This makes the behavior corresponding to allow_small_energy == 0 the default, and removes that parameter.

PR checklist

• test suite needs to be run on this PR
• this PR will change answers in the test suite
• all functions have docstrings as per the coding conventions
• the CHANGES file has been updated
• if appropriate, this change is described in the docs

[maximumcats]

This addresses part of #702 but not all of it (reset_internal_energy is still a discrete routine).

[zingale]

Note: this seems to dramatically help the Sod stellar problem (Sod_stellar-test1-2d):

development:

this PR:

[maximumcats]

I had missed that SDC called ca_reset_internal_e directly. So I moved the actual implementation to a separate interface that takes a box and an Array4, and then implemented both the MultiFab interface and that call from SDC with it. Please retest.

[zingale]

here are the tests: http://groot.astro.sunysb.edu/Castro/test-suite/gfortran/2020-03-15/index.html