Fixed some documentation and started documenting command line options
for glue scripts.
Added a few more command line arguments. Found out that I will need to
reorganize the glue scripts documentation because cmdoptions conflict
with each other in different sections. Added argparse group for the -f
and -d flags as well as an option keyword argument to the main method
that can be used in the future for testing.
Added glue script command line options including new directory structure
to separate the glue script documentation.  Added SSEC logo and favicon.
updated rescaling documentation
added -R to the mutually exclusive group, otherwise it doesn't work
Removed ubyte_filter and uint16_filter, they are replaced by
convert_to_data_type in the dtype.py module.
Moved definitions from developers guide to a glossary page. Added a
global include file to all files so that if I have any global
definitions I can put them in that file in the future. Also added
common_opts and global to the exclude pattern list and removed the
orphan directive.
Added a few glossary terms. Moved backends to a subdirectory. Cleaned up
and clarified some of the chain documentation.
Added constants documentation for a friendlier command line experience
when users get to that level of complexity. Fixed some typos.
Moved tests documentation to their own directory, making the
installation documentation a TOC pointing to those pages. Also changed
the 2 v2g tests into one basic test (scripts still need to be changed)
Updated test scripts to reflect the v2g tests being in one package.