datetime branch: moving most remaining datefmt-related calls from controllers to templates (milestone, changeset, timeline)
And also:
- fixed a small bug for the date format hints (was visible for the datetime hint)
- [http://blogs.law.harvard.edu/tech/rss#optionalChannelElements <pubDate> in RSS 2.0 feeds] should use `http_date`
- also use `http_date` in revision log text format (i.e. Changelog format)
