Bump versions

Mostly bumping versions to latest, including restlet 2.1.1 that is out of the release candidate phases now.

In terms of repositories I removed aduna snapshots, as we won't be requiring that anymore now. 2.6.10 has not been deployed to central yet (should ask if that can occur), so aduna releases is still required. Fortytwo.net repository is still required for the rdfjson test resources jar. That could be deployed to central to remove that reliance.

As far as I know, the Restlet team are not in any hurry to deploy to Maven Central. They have in their minds that they need to keep maven.restlet.org (even though it falls over every other day under the request load) [1][2]. Hence maven.restlet.org will need to be there for the foreseeable future, but that may not stop you deploying to central. I think they may have given up on completely restricting the use of repository elements in pom.xml files that are deployed to central, although it is still in the guidelines.

[1] https://github.com/restlet/restlet-framework-java/issues/481
[2] https://issues.sonatype.org/browse/OSSRH-1879