(From the user feedback interview.)
User should be able to see actual data than just the numbers. This could be by clicking on the table cells or in some other way.
Basically add a div in each table cell and populate it on demand (see [this](https://stackoverflow.com/questions/3897396/can-a-table-row-expand-and-close) for example). We can perhaps show a loading animation if it turns out to be slow. Note:
* The entire row will be clickable and we add the collapse/expand markers on the left to let people know the rows are expandable.
* Multiple rows can be expanded at the same time.
* Show a sane number of rows (say 10 for starters) and make the div scrollable.
* Totals row is expandable as well.
* User names and page titles are links (all left aligned in the div).
I think it makes sense (with this UI in mind) to go with Leon's idea in T182885#3949875 to show participants, new editors and retention on per-wiki basis. This also came up in a one of the user interviews where a program organizer would like to keep track of which participants are working on which wikis.
I would however split that into a separate task if we decide to go with it.