NewFeatures: Chronological entries

New: /oldest/ virtual directory restriction

DWiki has long been able to give people the latest N things in a virtual directory context (as latest/<N>). Now it can give them the oldest N things, using the obvious syntax: oldest/<howmany>.

Just to show off, ranges properly convert themselves into 'oldest/<N>' at the end of their run, just as they convert themselves into 'latest/<N>' at the start.

Documentation has been updated appropriately.

New: Better Last-Modified handling

Over the past while it has become increasingly obvious that it's useful for as many responses as possible to carry a Last-Modified: header. (The last straw was wanting Google's index to show modification dates for DWiki pages.)

My reason for killing Last-Modified: was so that things like logging in and logging out, which can't be reflected in the timestamp, would still have conditional GETs be served new pages. But since the conditional GET logic is in DWiki itself, I can have DWiki be smarter about it.

DWiki now separates the page timestamp from the idea of whether the page timestamp is reliable or simply vaguely useful information. The page timestamp will always be served if it exists at all, but conditional GETs only look at the page timestamp if it's reliable (which means that if authentication is on, the answer is generally 'not').

This should work much better.