Add tags into the document view

Currently, the document view on mobile doesn't include tags.
This information is useful, especially during demo of mobile and nuxeo vision (upload an image to nuxeo > show auto tag).

Included :

• avg. of 5/6 tags
• Listed tags (under title , author and dates)
• pattern when no tags are displayed
• case of many tags (>20) : how do we overflow

Out of scope (but should be in mind)

• Add a tag
• Click on a tag for actions (search this word...)