Adding sea ice formation flux.

This flux is called the q-flux in POP terms, but it computes the
formation of frazil ice on the ocean time steps.

Currently it's using a hard-coded freezing temperature of -1.8C, and
hard-coded density values which are provided through mpas_ocn_constants.
Fixing some small issues:

Allowing the unit numbers to start at 0, for the case of stderr.

Uncommenting out the 360day calendar.
Cleanup of some comments for coupled forcing.
Fixing io type issues.
Allowing file redirection within CESM.

CESM expects each component to write to a specific file, and it defines
the unit number that this file uses.

This commit fixes issues related to this.