Merge branch 'update_thomp_aer_metgrid' into develop (PR #201)

Merge branch 'update_thomp_aer_metgrid' into develop (PR #201)

This merge updates existing METGRID.TBL entries and adds new METGRID.TBL entries
for the Thompson AA microphysics scheme.

The changes in this merge complement WRF PRs #1567 and #1616 in order to clean
the logic in dyn_em/module_initialize_real, enable more flexibility when pre-
processing first guess aerosol fields (e.g., GEOS-5) for the Thompson Aerosol-
Aware scheme (mp_physics=28), and handle processing of black carbon aerosol and
biomass burning emissions.

Here is the text taken from WRF PR #1567:
Modifications have been made to the METGRID.TBL file to simplify the subsequent
logic in the real program's dyn_em/module_initialize_real. Specifically, we:

 * replace FLAG_QNWFA and FLAG_QNIFA with FLAG_QNWFA_CL and FLAG_QNIFA_CL, respectively, in the W_WIF_DEC and I_WIF_DEC entries, where “CL” stands for climatology;
 * add FLAG_QNWFA and FLAG_QNIFA to the QNWFA and QNIFA entries, respectively, for the first guess aerosol arrays;
 * add entry P_WIF to give the user the option to interpolate the first guess aerosol using the native pressure levels of the host model;
 * use num_wif_levels for any z dimension associated with the aerosol field entries (climatology or first guess);
 * add surface aerosol emission arrays QNWFA2D and QNIFA2D to be processed.

Here is the text taken from WRF PR #1616:
We add entries to METGRID.TBL to handle the black carbon aerosol category in
addition to biomass burning emissions. Specifically, we:

 * add monthly climatology entries for black carbon aerosol (B_WIF_*) which generate FLAG_QNBCA_CL for processing in real
 * add first guess entry for black carbon aerosol (QNBCA) which generates FLAG_QNBCA for processing in real
 * add first guess entry for anthropogenic emission of black carbon aerosol (QNBCA2D) which generates FLAG_QNBCA2D
 * add first guess entries for biomass burning emissions of organic carbon (QNOCBB2D) and black carbon (QNBCBB2D) which generate FLAG_QNOCBB2D and FLAG_QNBCBB2D, respectively

Note that the new .dat file for monthly GOCART climatology is hosted on Google
Drive: https://drive.google.com/file/d/1BYflyu65kP5giRYbTzKo6y4iSnTfb1Fw/view?usp=sharing

* update_thomp_aer_metgrid:
  Updating/adding METGRID.TBL entries for Thompson AA microphysics scheme