REP-702: Added needed tag for rpm plugin. Added artifact dir for license...

... file paths.
Should these guys be empty?

The XSD for this plugin has the following description:
"<description>The package group for the package.</description>"

... and the web documentation states:
"*group*
A string which identifies the software group for this package. This can be used by GUI tools to group packages for display. Check the RPM documentation (installed in /usr/share/doc/rpm-version/GROUPS on most Linuxes) for a list of current groups."