Add support for command line arguments and usage of "Config" module.

guardian now can be called with some additional command line arguments, like
"--config" to specify a different config file than the default one. The optoions
"--help" and "--vesion" will display some help texts and version informations on
the console. The "--foreground" option is not supported/implemented yet and will
be used to keep the process in the foreground and not fork into background at a later
time.

The "Config" module now also is used to get all settings from the config file and
store them into a hash called mainsettings for a later usage.

Signed-off-by: Stefan Schantl <stefan.schantl@ipfire.org>