Add support to schema based indexes and constraints

[ppyague]

Add support to schema based indexes and constraints, a feature that was introduced in Neo4j 2.0.

http://docs.neo4j.org/chunked/stable/rest-api-schema-indexes.html
http://docs.neo4j.org/chunked/stable/rest-api-schema-constraints.html

Thanks in advance,
Regards.

[versae]

I will try to include this in the next release. Thanks!