WIP: Multimedia Image API & IIIF Image API

**How we will restrict access to files?**
* Just check if the user  `invenio.modules.documents.api.Document`.`can_access` the document which contains the image?
* Serve images over invenio's oauth shield?
* Any other option :) ? ? ? ? 

**Notes**
If we go for the  1st option, it's better to move the IIIF Image API to the `invenio.modules.multimedia.views`


WIP of #1760