added kmltools_module.rst
more dtopotools2 documentation
Created doc/doc/extra_files directory for files that should show up in root of clawpack.github.io, and modified conf.py to add this directory in html_extra_path
Merge branch 'extra_files' into release_5.2.1

* extra_files:
  Created doc/doc/extra_files directory for files that should show up in root of clawpack.github.io, and modified conf.py to add this directory in html_extra_path
changed copyright date