Bugfix: Sorted collaborators column, deduplicate public entry

The collaborators column that appears in the "shared with others"
section are now sorted: first by share type (user, group, link, remote) and then by
display name using natural sort.
Additionally, if there is more than one public link for the resource, the text "Public"
only appears once in the collaborators column.

https://github.com/owncloud/web/issues/3137
https://github.com/owncloud/web/pull/3171
