Add "Logger" module.

Add "Logger" module.

This module is responsible for logging any messages which are generated by
guaridan or one of its submodules during runtime and displays them on the
console or send them to the syslog.

When using the logger module, it has to be initialized as an object, which calls the
"New" function and requires the following settings:

* LogLevel - which has to be "off, err, info or debug"
* LogFacility - which currently supports "console or syslog"

After that, logging can be done, by using the "Log" function on the object, by providing
the type of the message (LogLevel) and the message self.

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