Implement loading LDBC update stream CSVs to Neo4j

[szarnyasg]

Ideally, each of these load specifications could be translated to a set of simple Cypher queries (CREATE and MATCH ... CREATE), so we could execute them on both ingraph and Neo4j.

(Note: it will not be fast.)

[szarnyasg]

Note: the updates for the LDBC BI benchmarks are not yet worked out -- this is planned for Q3/Q4 2018.