Future Changes from wgrib2 v3.0.2 to v3.1.0

Big changes .. many inventory changes
1. wgrib2 upto v3.0.2 used NCEP web pages for table descriptions (scripts by M. Schwarb)
2. wgrib2 v3.1.0+ uses the WMO github for table descriptions (except field names) (scripts by M. Schwarb)
3. updated NCEP, ECMWF and DWD field names
4. old inv: :(chemical name): new inv: :chemical=(chemical name):
5. old inv: :process (number): new inv: :process=(number):
6. previous two changes are to make inventory consistent with -set_metadata
7. more compatibility for -set_metadata (wgrib2 file >inv; wgrib2 file -set_metadata inv)

Fix for PNG decoder
1. Can now handle PNG compressed grib files that use a bit depth of 1, 2 and 4
2. previously library could only handle 8 and 16 bit depths

Other Changes
1. Public release source code, wgrib2.tgz, is now compatible with a BSD-varient tar
2. -reset_delayed_error: remove writes to stdout
3. -ndates: removed limit on size of output
4. nearest neighbor for global Gaussian grid is now a calculation rather than search
5. bug fix in -import_grib and -import_grib_fs when main input is an incorrectly encoded NCEP constant field,
   the message read by -import_grib and -import_grib_fs will be incorrectly fixed.