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

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>