Fixed a bug that caused exceptions in the case of a vertex property with a cardinality other than single

Allow the value to a setter to be null

Fixed a bug that caused exceptions in the case of a vertex property with a cardinality other than single

Updated to not throw when returning a single item (this can just return null as frames did) and added a test

This simply unlinks the vertex in the case where the passed in vertex is null. This is similar to the frames behavior.

add information about support JanusGraph

ISSUES CLOSED: #27