On the Recent Changes page, I should be able to step back through time

Summary: That is, it should start out by showing, eg, the most recent month, and have a button that lets you go back a month at a time.

Eventually, we should enable you to choose a date range on-page, but one thing at a time.

This probably requires an enhancement to use page params for the stepping back, at least initially. (Although ideally this should happen on-page.)

Really ideally, the display of Recent Changes should be an infinitely-scrollable list. But that's likely to take a while.