base: pre-1900 publication date fix

* Fixes issue in JSONAlchemy configuration for publication dates
  prior to 1900 due to use of strftime.

Signed-off-by: Lars Holm Nielsen <lars.holm.nielsen@cern.ch>
global: update Invenio tracking branch

* Changes branch from zenodo/invenio-op@pu-zenodo-next to
  zenodo/invenio-op@pu-zenodo after the recent merge

Signed-off-by: Lars Holm Nielsen <lars.holm.nielsen@cern.ch>