SWORDv2 version for DSpace4

This PR provides the new version of the DSpace SWORDv2 implementation.

It is dependent on a new version of the Java server library:

https://github.com/swordapp/JavaServer2.0

Which is currently being prepped for maven central.  There is an open issue at the Sonatype OSS Repository for its inclusion:

https://issues.sonatype.org/browse/OSSRH-7529

Any tips or assistance in getting that dependency deployed would be welcome, as I'm new to maven deployments and it seems to be very long-winded!

Let me know what you need from me, otherwise, to smooth the contrib of this code.

Cheers,

Richard