Merge branch 'jonbob/mpaso/support-salinity-restoring' (PR #1419)

This PR adds salinity restoring to C- and G-cases, when the appropriate data
file is available, through namelist and streams modifications. It adds a new
ocean bld variable, ocn_forcing, that has three valid options: active_atm;
core_forced; and core_forced_restoring. For grids with a valid monthly
salinity-restoring file (currently oEC60to30v3 and oRRS18to6v3), modifications
are made to mpas-o_in, streams.ocean, and mpas-o.input_data_list files. For
grids which do not yet have the required file, a warning is issued during the
case setup and the namelist/streams/input_data changes are not applied. This PR
also turns on the diurnal cycle for all C- and G-cases, regardless of the
availability of salinity-restoring files.

Note: because this codebase fails exact restart tests, it is off by default,
      even for situations in which it is fully supported. It will be made
      active by default once it does restart correctly (to be tracked by a
      separate issue).

Scripts tested with SMS.T62_oEC60to30v3.GMPAS-IAF.edison_intel and
SMS.T62_oQU240.GMPAS-IAF.edison_intel.

Salinity-restoring namelist parameters tested for 250+ years with
20170320.beta0.GMPAS-IAF.T62_oECv3.anvil.

[NML]
[BFB]

src/components/data_comps/datm/cime_config/namelist_definition_datm.xml

@@ -1944,6 +1944,7 @@
            steps, which is undesirable unless we truly want linear interpolation
            between multiple input values -->
       <value stream="topo.observed">lower</value>
+      <value stream="CORE2_IAF.GISS.SWDN">coszen</value>
     </values>
   </entry>