Cypher support for graph databases

[Mike Thomsen <mi...@gmail.com>]

I fired off the PR for Cypher support a few hours ago and looks like all of
the basic tests passed against the 1.9.X codebase. This is a refactoring of
Mans Singh's original contribution for Neo4J support to make it use
controller services that abstract away the underlying Cypher
implementation. I tested it against Neo4J and JanusGraph 0.3.1 w/
OpenCypher, and both looked good.

PR is here for anyone interested:

https://github.com/apache/nifi/pull/3318

If we could get a code review going post 1.9.X I'd appreciate it, and I'm
sure Mans would too.

FWIW, I've also got some pretty detailed sketches for how to make the
record API work with graphs that I can start laying down if/when this gets
merged.

Thanks,

Mike