Fix for latex in Springer titles and abstracts.

* Removes completly latex part from records in Springer collection.
Check for erratum, addendum and editorial.

* Adds a bibcheck plugin to go through all records and find erratas,
  addendums and editorials. If the record meets the criteria then it
  gets an additional 980__c tag with corresponding name: ERRATUM,
  ADDENDUM, EDITORIAL.