pidstore: module separation
pidstore: module separation

* INCOMPATIBLE Separates PIDStore module to independent
  Invenio-PIDStore package.

Signed-off-by: Jiri Kuncar <2bdffcb416fed3002465740d19a053a39918cbe5@cern.ch>

inveniosoftware/invenio-base,inveniosoftware/invenio-base,tiborsimko/invenio-base,tiborsimko/invenio-base