Adding a pagination

This adds a pagination to the starter kit because now we can, on both the index and the search page.

Two questions:
 * Do we want to add a pagination in the starter kit? I think it makes sense to do it, but can you ask Sadek and Guillaume what they think of it?
 * There's probably a way to "D.R.Y." that better, but I couldn't figure out how. I was thinking of using a partial, but you need to use different programmatic stuff like `search_path(q: params[:q], ref: @maybe_ref, page: j==1 ? nil : j)` (`j` changing often in the partial, as it is being looped upon). I thought it looks like I could pass that as a block, but blocks in partials look more like "subpartials" than anything else (they seem to be view, not programmatic stuff). What do you think?