finalize 0-layer thermo and cesm ponds deprecation in Icepack

[eclare108213]

• Short (1 sentence) summary of your PR:
  Removes all ifdef options allowing 'undeprecation' of 0-layer thermo and cesm meltponds, and updates documentation
• Developer(s):
  @eclare108213 @dabail10
• Suggest PR reviewers from list in the column to the right.
• Please copy the PR test results link or provide a summary of testing completed below.
  Full test suite on cheyenne, intel is bfb. https://github.com/CICE-Consortium/Test-Results/wiki/icepack_by_hash_forks#ef0efc78666d7b7451eb86a76e2eb0e35f50156a
• How much do the PR code changes differ from the unmodified code?
  • bit for bit
  • different at roundoff level
  • more substantial
• Does this PR create or have dependencies on CICE or any other models?
  • Yes
  • No
• Does this PR add any new test cases?
  • Yes
  • No
• Is the documentation being updated? ("Documentation" includes information on the wiki or in the .rst files from doc/source/, which are used to create the online technical docs at https://readthedocs.org/projects/cice-consortium-cice/.)
  • Yes
  • No, does the documentation need to be updated at a later time?
    • Yes
    • No
• Please provide any additional information or relevant details below:

[dabail10]

I think that hs0 is only used for the CESM ponds. hs0 is used to initialize the snow fraction in shortwave_dEdd_set_snow which is still called in the level ponds. However, with hs0 set to 0, the snow fraction will be set to 1 and then it is recomputed using hs1. Not sure if this subroutine should even be called.

[eclare108213]

@dabail10 I'll take a look, thanks for the insight.

[eclare108213]

I need to fix the formatting in the documentation, both here and in CICE-Consortium/CICE#787

[eclare108213]

Unfortunately LANL is blocking my access to the Icepack documentation generated from this PR. Could someone take a look at section 2.7 (there should be a new subsection called 'Snow fraction') and the bottom of the variable index, and let me know if they formatted okay?

[apcraig]

Everything looks good to me. I tried to grab the pdf to send to you, but I think pdfs are only generated with a tag or something.

[eclare108213]

I reverted the default/initial values of hs0 in both Icepack here and CICE CICE-Consortium/CICE#787, but otherwise did not alter the documentation updates in either PR, pending resolution of CICE-Consortium/CICE#635. This PR partially addresses the confusing documentation called out in that PR.

[apcraig]

Test results for cheyenne intel are here, https://github.com/CICE-Consortium/Test-Results/wiki/icepack_by_hash_forks#ef0efc78666d7b7451eb86a76e2eb0e35f50156a. Updated PR too.