registry: move to separate package Flask-Registry
registry: move to separate package Flask-Registry

* Moves Flask-Registry to a separate external package.

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

NOTE: beware, patch amended by Tibor to use new file names

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