Merge pull request #303 from fvitt/dep_data_file

Description of changes

This moves the hard-wired data from seq_drydep_mod to an input file that can be easily replaced to provide flexibility.
Specific notes

This PR needs to be coordinated with
ESCOMP/CAM#602

See relevant discussion in:
ESCOMP/CESM_share#8

Contributors other than yourself, if any:

CMEPS Issues Fixed (include github issue #):
ESCOMP/CESM_share#8

Are changes expected to change answers? (specify if bfb, different at roundoff, more substantial)
bfb

Any User Interface Changes (namelist or namelist defaults changes)?
Added dep_data_file (in drv_flds_in) for the path of the input data file containing Henrys Law coefficients
Testing performed

Testing performed if application target is CESM:

(recommended) CIME_DRIVER=nuopc scripts_regression_tests.py

    machines: cheyenne, izumi
    details (e.g. failed tests):

(recommended) CESM testlist_drv.xml

    machines and compilers:
    details (e.g. failed tests):

(optional) CESM prealpha test

    machines and compilers
    details (e.g. failed tests):

    aux_cam tests
        machines and compilers: cheyenne-intel, izumi-gnu, izumi-nag
        details (e.g. failed tests):

Testing performed if application target is UFS-coupled:

    (recommended) UFS-coupled testing
        description:
        details (e.g. failed tests):

Testing performed if application target is UFS-HAFS:

    (recommended) UFS-HAFS testing
        description:
        details (e.g. failed tests):

Hashes used for testing:

CESM:

    repository to check out: ESCOMP/CESM.git
    branch/hash:

UFS-coupled, then umbrella repostiory to check out and associated hash:

    repository to check out:
    branch/hash:

UFS-HAFS, then umbrella repostiory to check out and associated hash:

    repository to check out:
    branch/hash: