Added REST test for GraphRepositories
DATAGRAPH-388 Support for Labels (indexes, queries etc)

* @Indexed(indexType=LABEL)
* added template.isLabelBased(), indexInfo.isLabelBased() and TRS.isLabelBased()
* already reworked some of the derived finders to consistently use a start-less syntax wherever possible
* first stab at dynamic Labels with @Labels and LabelFieldAccessorFactory