add Date: field to Packages files

[Dan Jacobson <jidanni@jidanni.org>]

Say, perhaps a "Date:" field could be added to Packages files.
I mean even dog food has the date stamped on it these days.
Even my crumby message has a Date: field.
Sure, as your eyes scan the MD5sum: field, the package's DNA is
registered in your brain. But us old fashioned types would still like
a Date: field.
> Well Jacobson, the date can be clearly seen at http://.../pool/n/norbowitz
But Mom said no more searching the web for dates, so now I'm offline.