GBBEPx version 4 will replace current version 3 product

[lipan-NOAA]

The script of "exglobal_prep_chem.sh" need to be updated to digest this change.

This updates include three parts:

1. read in GBBEPx version 4 inputs, the details of file name changes for GBBEPx version 4 can be found in the google document "https://docs.google.com/spreadsheets/d/11cKJk-CGnbwo2w6NbjUj0-RG81YzsgTykbPfhv5bR20/edit#gid=0";
2. update MODIS fire inputs because file names have been changed;
3. disable wf_abba data since data is no longer available at /dcom;