harvestingkit: Adds delivery/doi-to-package data

* Adds the variables packages_delivery and doi_package_name_mapping
  to springer_package.py and oup_package.py to store the time a
  package has been received and to map a doi to a package name.

Signed-off-by: Martin Vesper <martin.vesper@cern.ch>
Merge pull request #99 from mvesper/dates_aggregation_springer_oup

harvestingkit: Adds delivery/doi-to-package data