General update

Updated component in compliance with DataModel 1.0 aiming at being able to properly manage Fingerprint, Item and Property objects in front-end code. Functionality supposed to be obsolete (e.g. toJSON(), newFromJSON()) is removed in favour of using the wikibase.serialization component (see https://github.com/wmde/WikibaseSerializationJavaScript/pull/6 for corresponding changes to that component).