changes to FAFMIP/OMIP process tendency diags

Steve and I would like to make some changes in the process-based tendency
diags requested by FAFMIP and OMIP. I attach a revised version of the FAFMIP
spreadsheet, with the changes made in the New Variables and New Variable
Groups. The changes are the same (I hope!) for the three sets of variables
opottemp*, ocontemp* and osalt*. Each set appears once in the New Variables
spreadsheet and twice in the New Variable Groups spreadsheet. In each set,
the changes are:

Replace the quantity having shortname Xadvect with Xrmadvect, whose standard
name will be X_due_to_residual_mean_advection, instead of X_due_to_advection.
This is because some models can't diagnose (resolved) advection and
parmeterized eddy advection separately. The residual mean is their sum,
and we request the latter separately for those models which can supply it.

Rename Xeadvect to Xpadvect, for the quantities with standard names
X_due_to_parameterized_eddy_advection. This is for consistency with other
short names that correspond to these.

Delete the requests with short names Xpmadvect and standard names
X_due_to_parameterized_mesoscale_advection. This is because
padvect = pmadvect + psmadvect
so if we have padvect and psmadvect, we don't need to ask for pmadvect too.
NB we are keeping pmdiff - that's different.

This discussion has been closed.