D-Net

#955 fixing reference raw text generation for pretty printed NLM documents

#840 renaming DeduplicationMapping to more generic IdentifierMapping

#840 moving IdentifierMapping from importer to common package

#840 renaming DeduplicationMapping to more generic IdentifierMapping

#757 adding reducing phase for filtering out pmids by article type, mapping phase groups PmidMapping objects by pmid and at reducer phase duplicates will be filtered out

#757 introducing article type extraction along with unit test. Article type will be required for filtering out pmc duplicates and leaving only proper types

fixing sourceDocumentId which is now extracted from input DocumentText record conveying NLM

#757 fixing pmc citation matching test by providing proper input