global: file renaming

Signed-off-by: Tibor Simko <tibor.simko@cern.ch>
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
global: move to new code structure

Co-authored-by: Esteban J. G. Gabancho <esteban.gabancho@cern.ch>

NOTE: beware, patch amended by Tibor to use new file names
global: move to new code structure

Co-authored-by: Esteban J. G. Gabancho <esteban.gabancho@cern.ch>

NOTE: beware, patch amended by Tibor to use new file names
global: move to new code structure

Co-authored-by: Jiri Kuncar <jiri.kuncar@cern.ch>
Co-authored-by: Esteban J. G. Gabancho <esteban.gabancho@cern.ch>
Co-authored-by: Adrian-Tudor Panescu <adrian.tudor.panescu@cern.ch>

NOTE: beware, patch amended by Tibor to use new file names
global: print function usage
global: `has_key` to `in` operator fix

Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>
connector: InvenioConnector URL validation

* InvenioConnector will now throw an InvenioConnectorServerError
  exception is the given URL is invalid.

Signed-off-by: Graham R. Armstrong <graham.richard.armstrong@cern.ch>