The program 'afni_refacer2' is a slightly updated version of the
original @afni_refacer_run program.  The changes mostly occurred under
the hood, as it were, to make the guts of the program easier to
maintain.  The options, behavior and outputs stayed very similar.

Some new de/refacing modes were added, the '-mode2_*' ones.  These
were added to provide some more training/validation/testing cases for
3dBrainTeaser.  These new modes are not generally recommended for
users.

By default, the new afni_refacer2 uses slightly modified reference
dataset shells. Importantly, the default shells will remove more face
and ears, which was viewed as desirable. (See below for other minor
improvements in them.)

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New de/refacing shells

One important change was that the default de/refacing shells changed,
to be the 2.0 and 2.1 versions. These were created from the original
versions using this new script:

    adjunct_refacer_make_master_addendum2

This script runs without any options, and just assumes that these two 
datasets are present+loadable:

    afni_refacer_shell_sym_1.0.nii.gz
    afni_refacer_shell_sym_1.1.nii.gz

The script runs through a lot of rigamarole and intermediate datasets, and
creates:

    afni_refacer_shell_sym_2.0.nii.gz
    afni_refacer_shell_sym_2.1.nii.gz

These shells have the slightly improved properties of not having tiny
holes.  They are just cleaner versions of the original ones.  They
don't materially change the de/refacing.
