D-Net

#1017 introducing new PMC metadata ingestion currently extracing references, journal and pages fields.
Replacing DOM/XPath based citations ingestion with much faster SAX version. Changing pmidtooaid transformer utilizing ExtractedDocumentMetadata instead of parsing XML file. Enabling PMC metadata ingestion in common/import.

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

introducing embedded integration test entry

#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