Update Janusgraph to 0.5.0 in traversal

Update Janusgraph to 0.5.0 in traversal

- update Janusgraph to 0.5.0 + tinkerpop to 3.4.13
- do not use pagination methods from HttpEntry [1]
- introduce WebTestClient as a way to more elegantly declare http requests and assertions

[1] pagination is still done on the client-side in this service.
This change just removes the usage of methods of HttpEntry that effectively do a List.subList
and that will be removed from HttpEntry shortly after

Issue-ID: AAI-3902
Change-Id: I446f092048b9e2be7314ed32ab3de5d5e1e1689d
Signed-off-by: Fiete Ostkamp <Fiete.Ostkamp@telekom.de>