Update dependencies version; prepare for maven move

[om26er]

• Updates versions for https://github.com/crossbario/autobahn-java/issues/521
• Minor work towards https://github.com/crossbario/autobahn-java/issues/522 (will do another PR during the weekend)

[oberstet]

^ the CI here is still Travis, which we canceled, as we moved (well, want to;) everything to GH actions