hgweb: move HTTP content types out of header templates
This removes the ability for templates to add custom HTTP headers, which can
easily be re-added if someone needs it. Thanks to asak for repeatedly reviewing
this patch and helping to iron out the quirks.
import doctest
import mercurial.changelog
# test doctest from changelog
doctest.testmod(mercurial.changelog)
import mercurial.httprepo
doctest.testmod(mercurial.httprepo)
import mercurial.util
doctest.testmod(mercurial.util)