Allow to pass extra configuration options when creating indexes

This allows clients to specify custom lucene analyzers and possibly tweak
the indexes with future options provided by neo4j/lucene. The current ones
can be seen at http://docs.neo4j.org/chunked/stable/indexing-create-advanced.html
Merge pull request #133 from continuum/extra-config-for-create-node-index

Allow to pass extra configuration options when creating indexes