global: new code structure
- Adds Sphinx documentation.
- Moves Jinja2 templates to the new code structure invenio/modules/<name>/templates/<name>/index.html.
- Adds new tag module developed by Krzysztof Lis <krzysztof.lis@cern.ch>.
Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>
Co-authored-by: Esteban J. G. Gabancho <esteban.gabancho@cern.ch>
Co-authored-by: Krzysztof Lis <krzysztof.lis@cern.ch>
Co-authored-by: Adrian-Tudor Panescu <adrian.tudor.panescu@cern.ch>
NOTE: beware, patch amended by Tibor to use new file names