PLUMBER2 site usermods: Get values from .csv file

[samsrabin]

There are a ton of PLUMBER2 user mod directories with things like this in shell_commands:

CTSM/cime_config/usermods_dirs/clm/PLUMBER2/AR-SLu/shell_commands

Lines 2 to 7 in 7409d32

	./xmlchange PTS_LON=-66.459808
	./xmlchange PTS_LAT=-33.464802
	./xmlchange DATM_YR_END=2010
	./xmlchange DATM_YR_START_FILENAME=2010
	./xmlchange START_TOD=10800
	./xmlchange ATM_NCPL=48

Instead of hard-coding these, most could be determined programmatically from tools/site_and_regional/PLUMBER2_sites.csv. This would allow the CSV file to serve as the single source of truth, avoiding possible errors due to typos in the shell_commands files.

[wwieder]

@samsrabin , I think this is done with python/ctsm/site_and_regional/plumber2_usermods.py, which reads in the csv file to create the custom plumber2 usermods. Does this address the issue, or were you thinking of something else?

[samsrabin]

Ahhh, right you are!