fixed some errors found in the documentation and fully updated the internal
commands docs as well.
also updated the internal module to now respond to KILL_CMD so it can now be
signaled to terminate gracefully.
-the add_mod command now requires the -mod_path argument as it should.
-the session now filter out bad NEW_CMD frames based on bad command names and incorrect
frame sizes.
-modules running in list mode can now send ERR frames to the session to log error
messages to the host database.