Add support for creating a fedora RPM package with maven

Note: This has been disabled by default and is therefore not included in a
standard build. The main reason for this is, that you need to have a RPM
binary and the rpm development packages installed, which is not the case
on many systems.

The package contains an init.d-script as well as systemd configurations.

You can build your own RPM package simply by running 'maven rpm:rpm'