* Simplify the nonlocal increments in vertFPMix;
* Pass boundary layer depths to the RK2 and add consistency check
  to make sure FPMix is always used with SPLIT;
* Add the capability to mix down the Eulerian gradient instead of
  the Lagrangian;
* Make a minimum set of FPMix diagnostics available.

Changed the empirical coefficient for non-local momentum mixing (Cemp_NL)
from a hardcoded value to a user-defined parameter.

This is done for DIC, ALK, and related tracers.
This mimics uptake and release of these tracers by sea ice.

* Modify NUOPC cap to accept separate glc runoff fluxes
* (1/2) Add separate fluxes for glc runoff. (2/2) Add heat content fields for lrunoff_glc and frunoff_glc.
* fix merge bugs and add more glc runoff diags
* enable glc runoff flux only if use_glc_runoff is present
* add ALLOW_GLC_RUNOFF_DIAGNOSTICS param to control whether to allow separate glacier runoff fluxes.

correct some indentation issues

MARBL: convert salt_flux to tracer flux and add to STF

Updated MAX_LAYER_THICKNESS to use longString for
handling extended path+filename.