different license representations in different oc-instances

[mirjan-hoffmann]

The representation of the license differs from instance to instance. For example UOS uses representations like CC-BY-SA, while TIHO uses representations like Creative Commons 3.0: Attribution-NonCommercial-NoDerivs

Currently we need to add all the different representations in the allowedLicences list. Currently there is just a mapping for some representations to the edu-sharing licenses.

I think, it would be better to map the licenses from the oc-value to the edu-sharing representation first and afterwards check against the allowedLicences list. The mapping should be configurable as we can not know all values from all oc-instances.