adding testcase for GPNEO4J-20
neo4j: fix plugin tests
GPNEO4J-21 - Plugin fails to load in Grails 2.4.2

* Switching to context classloader for instantiating GraphDatabaseService
* GRAILS-11112 introduced a custom PropertiesEditor that converts property values to Strings - this is something we don't want here. Therefore reconfiguring the customEditors bean to its previous state