Updated the data API to include a new type of individual: the NewIndividual. This individual, identified by URI, is meant to represent a new resource that should be created by the application. The individuals will be identified with relative URIs, in contrast to ExternalIndividuals which will be identified by absolute URIs. These individuals will be generated during the lifting process, specifically during the processing a POST request. During the lowering process (GET operations) these individuals will be ignored, so triples having them as either subject and/or object will not me marshalled. The usage of URIs is now strict. ExternalIndividuals will only be allowed to be created with absolute URIs, whereas relative URIs will be enforced for NewIndividuals.