Fre cmor config exposed

[ilaflott]

this PR takes hard-coded values/args/assumptions of fre/cmor/cmor_mixer.py and attempts to make it less dependent on such "hidden configuration".

[ceblanton]

This looks like a quiet PR for a couple days. Is it ready for review?

[ilaflott]

draft PR status is "Hold" for now while we get other priorities/capabilities/issues straightened out.

[ilaflott]

# ----- \start consts
DEBUG_MODE_RUN_ONE = True

#
INPUT_READ_PS_FILE_VAR_NAME = 'ps'
OUTPUT_TEMP_DIR_NAME = 'tmp'

#
INPUT_READ_TAG_OCEAN_GRID_VAR = 'xh'
INPUT_READ_Z_AXIS_NAME = 'Z'

#
INPUT_READ_LAT_DIM = 'lat'
INPUT_READ_LAT_BNDS = 'lat_bnds'
INPUT_READ_LON_DIM = 'lon'
INPUT_READ_LON_BNDS = 'lon_bnds'
INPUT_READ_TIME_DIM = 'time'
INPUT_READ_TIME_BNDS = 'time_bnds'

#
INPUT_READ_AP_ZFACTS = ['ap','ap_bnds']
INPUT_READ_B_ZFACTS = ['b','b_bnds']

#
OUTPUT_WRITE_AXIS_LEVELS_NAME="alternate_hybrid_sigma"
OUTPUT_WRITE_AP_ZFACTS_NAME = "ap"
OUTPUT_WRITE_B_ZFACTS_NAME = "b"

#
OUTPUT_WRITE_AXIS_LEVELS_HALF_NAME="alternate_hybrid_sigma_half"
OUTPUT_WRITE_AP_ZFACTS_HALF_NAME = "ap_half"
OUTPUT_WRITE_B_ZFACTS_HALF_NAME = "b_half"

#
INPUT_ACCEPT_VAR_DIMS = [3,4]
INPUT_ACCEPT_VERT_DIMS = ['plev30', 'plev19', 'plev8','height2m', 'level', 'lev', 'levhalf']

#
OUTPUT_PS_VAR_NAME = 'ps'
OUTPUT_PS_VAR_UNIT = 'Pa'

here's the bit i cared about, it's also in the issue.