edpsciences_package: Astrophysics subject added

Signed-off-by: Georgios Papoutsakis <georgios.papoutsakis@cern.ch>
global: refextract indentifier added

* Adds the subfield 9995C9:refextract for
  references extracted with refextract.

Signed-off-by: Georgios Papoutsakis <georgios.papoutsakis@cern.ch>