invenio_package: new module

* Adds a new module for parsing and converting OAI-PMH
  (and non-OAI-PMH) MARCXML from Invenio instances to various
  formats.

* Adds new conversion filters for converting records between
  CDS and INSPIRE.

Signed-off-by: Jan Aage Lavik <jan.age.lavik@cern.ch>