#577 updating Citation namespace
#577 introducing common.citations.Citation schema
removing redundant ReferenceBasicMetadata and ReferenceMetadata definitions which are also available in standalone avdl definitions, replacing definitions with import statements.
removing deprecated PersonWithInferencedData avro schema
removing deprecated DocumentWithInferencedData and DataSetReferenceWithInferencedData avro schemas
#568 renaming Citations#sourceDocumentId field to Citations#documentId
#568 introducing CitationEntry and Citations schemas
rename a field