Create the 'About content' widget

There should be an aboutcontent widget that has 2 different tabs. The first tab is the Details tab and shows the metadata of the content (title, description, url, created by). When a description is not available, it should not be shown. The second tab is the Shared with tab and shows the list of members of the content.
Thinking about this a bit more, I don't think we can have `metadataUserPrefix` as a display option. There's no guarantee that the structure will be `Added by x` for all languages, so I think we'll have to have the HTML for the list item in the widget.