multimedia: IIIF Image API addition

* Implements the IIIF Image API.

* NOTE For more info please read <http://iiif.io/api/image/2.0/>

Signed-off-by: Harris Tzovanakis <drjova@cern.ch>
Reviewed-by: Jiri Kuncar <jiri.kuncar@cern.ch>

Conflicts:
	invenio/modules/multimedia/api.py