Store latest release date for packages.

[ADmad]

Allow sorting packages by release date.

[LordSimal]

should this be independent of the major/minor version?

[ADmad]

yeah just the date of the latest release regardless of the version

[ADmad]

I would also consider using the latest release date for default sorting order. It would give visibility to new packages and make users aware of new release for packages they are already using.