PropertyEdgeConverterManager

Since Neo4J uses the PropertyEdgeConverter (as it implements the CompositeAttributeConverter interface), we cannot define it as a singleton, as it requires to have a constructor. We want to be able to dynamically define converters for PropertyEdges that have more complex structures such as enums or custom classes, we need a singleton to be able to add the converters. Refer to the documentation of PropertyEdgeConverter to see which primitives are supported by default, and which require a custom converter.