Preliminarily adds the ability to turn off some coupled components for
the ensemble.

To enable this, many settings are moved out of `config.fcst` and into
`config.ufs` so they are calculated after any overrides of `DO_*` have
been made. Some settings also had to be moved out of `config.base` for
the same reason.

The name of the nems configure template used is converted from a
partial file name to the full file name. In anticipation of NOAA-EMC#1942, the
filename is assigned to a variable named `ufs_configure_template`,
though otherwise 'nems' is still used for filenames, etc.

Refs NOAA-EMC#1692

Copies the changes made to accomodate different coupling for ensemble
to the GEFS configs.

Refs NOAA-EMC#1692

Removes the old cpl validation script since the nemsconfigure string
is no longer used and replaces it with a check whether the specified
template file is readable.

Refs NOAA-EMC#1692

When creating the new cases to determine the nems configure template,
one was missed.

The variables added to config.aero were not being exported, causing
namelist construction to fail later.

The variables in `config.aero` are not set upstream, so there is no
reason to allow pass-throughs.

Renames the chem directory to gocart to be consistent with other
components.