feat: integrate with fuseki (graph database+api)

* feat: integrate with fuseki (graph database+api) streams
resolves apache/streams-activitypub#5 : **Add a graph module and a Webfinger implementation using jena graphdb binding**

- adds a real implementation of webfinger protocol which responds only to requests for entities that exist in the configured fuseki triple-store
- tests capabilities at the WebfingerApi Graph implementation level, and within the packaged webapp
- apache/streams-activitypub docker image now runs streams-activitypub-webapp and jena-fuseki2-webapp

Signed-off-by: Steve Blackmon <sblackmon@apache.org>
32 files changed