Added ReferenceListSerializer
Added ReferenceListUnserializer
Removed calls to Snak.toMap() and Snak.newFromMap()
Implemented StatementSerializer
Implemented StatementUnserializer
Added TermGroupSerializer
Added TermGroupUnserializer
Added TermGroupListSerializer
Added TermGroupListUnserializer
Added FingerprintSerializer
Added FingerprintUnserializer
Added StatementListSerializer
Added StatementListUnserializer
Added ClaimListSerializer
Added ClaimListUnserializer
Added SiteLinkListSerializer
Added SiteLinkListUnserializer