#56 Last-Modified HTTP header

[Steve Pugh]

The Last-Modified Date on content item is currently set
to the current time. This means from a cache's point of
view, content items always appear to be modified.

The following patch sets the Last-Modified header to be
the time the content item was actually modified. It
should make aplaws more effecient, espeically if aplaws
is used with a caching server like Squid.

[Steve Pugh]

last-modified-date patch