Idea: include setting various dates

[polyester]

There is currently no practical end-user way to manipulate the various dates (CreationDate, PublishingDate, EffectiveDate, ExpirationDate) on objects. Solutions rely on hacks & scripts. And this counts as 'metadata', so this package would probably be a good place to stick it in, instead of creating yet another package.

Will see what I can do, but first see if you would agree this is the right place.