Paginate recent changes

[sbrl]

On wikis that have been around for a while, the recent changes page starts to grow unwieldy. While the page can be generated by the server quickly, it's more of a problem for a human to understand and parse, and can be an issue for slower clients to render.

Additionally, we may want to look at turning off JSON_PRETTY_PRINT for recent-changes.json, since it's been working fine and there's not much of a reason to edit that file (unlike the pageindex).