DATAGRAPH-387: LabelTypeRepresentationStrategy

@jexp Initial LabelTypeRepresentationStrategy for comment. I have a Cypher and non Cypher impl for comparison purposes, classes named CypherBasedLabelingNodeTypeRepresentationStrategy (will be renamed to plain LabelingNodeTypeRepresentationStrategy) and CoreAPIBasedLabelingNodeTypeRepresentationStrategy. I will add some discussions at various points in the code which we need to chat about, but let me know what you think.