Linkbcs Standalone Script

[sshakoor1]

(This is the same as #820, just renamed as per request of @rtodling #820 (review))

The purpose of this PR is create a new linkbcs that is no longer a template file detemplated by gcm_setup, but rather a standalone python script ran via a config yaml. This new script should essentially be zero-diff from the old one.

To run, use $INSTALL_DIR/bin/linkbcs.py --config <USER_CONFIG>.yaml --timestamp <YYYY>-<MM>-<DD>T<HH>:<MM>:<SS> from inside the directory you want your symlinks to be created.

Here is a skeleton of what the config yaml should look like, along with valid options for each key:

platform: #nccs or nas
experiment_type: #GCM or ADAS
agcm_grid: #c12, c24, c48, c90, etc.
land_version: #icarus, icarus-NLv3, v12, v14
ocean_model: #data, mom6, MIT
ogcm_grid: #reynolds, merra-2, ostia, cubed_sphere_ostia, cubed_sphere_ostia_r21c
seaice_model: #cice4 or cice6 (this entry is only required for coupled ocean)
precip_correction: #True or False 
catchcn: #True or False
pchem_species: #ops, cmip, s2s, merra-2
install_dir: /path/to/your/install/dir

SOME NOTES:

• these entries are case sensitive at the moment.
• The install_dir should point to the directory your build of GEOS is installed in. For most people this will simply be .../<user_dir>/GEOSgcm/install/
• Right now only the year matters in the timestamp, but you still need to put entries for the time/month/day (they could all be zero).