[ALLI-2696] Fixed an issue that caused empty values to be indexed in publication year.
Fixed a longstanding issue that caused an error processing MARC records with 015 fields for deduplication.
Moved deduplication-related methods to their own class and made it possible to define the class used in configuration.
Added support for specifying which single-valued fields are to be included in merged records. Added support for adding the source id to merged fields.
Added support for using multiple background threads/processes in Solr updater.
Fixed a goof from removeFromDedupRecord. No more meaningless but heavy Mongo queries.
Added a couple of checks to checkdedup validation command.
Moved SolrUpdater to constructor parameter in DedupHandler.
Added a couple more checks dedup record verification. Fixed a logic issue that might have left records without dedup_id. Improved code a bit here and there.  Made renormalize only set update_needed if any of the dedup keys changed.
Added MARC 245c to getTitle(true) to improve its precision in sorting and deduplication.
NdlMarcRecord: Added indexing of 852 field.
Added a couple of sample entries to recordmanager.ini.sample
NdlMarcRecord: use textProper field instead of text field for holdings.
NdlMarcRecord: Added appending of source id to holdings_txtP_mv.
MarcRecord: Added sanity checks and logging.
Removed support for suffixed merged fields (a bad idea).
Code cleanup, removed a useless line.
Fixed updateDedupCandidateKeys to properly update keys for records that didn't previously have any.
Changed a couple of Mongo indexes to non-sparse since sparse causes problems with $exists:false queries.
[ALLI-2700] Fixed a problem that caused MARC subfield 0 to be included in Solr fields regardless of subfields selected. Also changed the MARC field handling functions to use more efficient key-based arrays for subfield selection.
Ndl records: added checks for invalid date ranges with start date later than end date.