Include docstrings (PEP8, PEP257) for module and all functions.
Separately, remove outdated section in comment at start of
module. Separately, remove unused global constant "usetunable".
Reviewed-by: George Melikov <mail@gmelikov.ru>
Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov>
Signed-off-by: Scot W. Stevenson <scot.stevenson@gmail.com>
Closes#6818