WIP: Multimedia Image API & IIIF Image API

after a discussion with @jirikuncar 

##### 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? 

Yes we should check if the user has access to this document. 

###### Serve images over invenio's oauth shield? 

Yes we should we should also include it to the oauth shiled.

~~**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
We have stopped using this format in favor of PEP257.

```python
"""Multimedia and IIIF Image APIs."""
```