RPZ: code updates and bug fixes #2

RPZ: code updates and bug fixes #2

 - feature: added "list" action
 - update: changed "cat << heredocs" to "echo > file"
 - update: remove path to executables
 - update: reformatted code and comments (tabs to spaces)
 - update: reworded some msg_log messages
 - update: change exit codes from "1" to unique exit code numbers
 - bug: added check for empty allow/block config file
 - bug: removed auth_zone_reload (had double reload for allow/block)
 - bug: change rpz config file to `chown nobody:nobody`
 - bug: change rpz config file to `chmod 644`

Signed-off-by: Jon Murphy <jon.murphy@ipfire.org>