Map multiple Shibboleth attributes to user attributes

Make it possible to match multiple Shibboleth attributes to MCRUser attributes.
Like this:

<attribute name="roles" mapping="eduPersonAffiliation">
<valueMapping name="employee">submitter</valueMapping>
<valueMapping name="student">reader</valueMapping>
<valueMapping name="member">reader</valueMapping>
</attribute>
<attribute name="roles" mapping="entitlement">
<valueMapping name="urn:uni-jena:iam:affiliation:Gastmitarbeiter">submitter</valueMapping>
<valueMapping name="urn:uni-jena:iam:affiliation:Gaststudent">reader</valueMapping>
</attribute>