tags: module externalisation to new package
- INCOMPATIBILITY Removes 'tags' module that has been externalised to separate Python package called 'invenio_tags'. Migration can be done by running pip install invenio_tags and adding 'invenio_tags' to PACKAGES.
Signed-off-by: Leonardo Rossi <leonardo.r@cern.ch>
Reviewed-by: Jiri Kuncar <jiri.kuncar@cern.ch>