Need to rework "most recent release" determination

The "download most recent release" link on a project's page has so far worked by fetching the latest date of a release. Since release dates have not changed after they were first created, a 4.6 release would always be later than a 4.5 one (presuming that the 4.5 branch was registered before the 4.6 one). But now that we're about to start changing dates every time a change is made, we'll get problems--when a 4.5 release is changed, its date will be the most recent, and so it will show up as the "most recent" version.

Maybe we need to use a combination of the 'created' and 'changed' values--the created for the determination of what version to use, the changed for the date to display to users.