hgweb: use generator to count parity of horizontal stripes for easier reading. - use web.stripes in all places and consistently - start with parity0 for lists generated in reverse (e.g. changelog)

#!/bin/sh

hg init dir
cd dir
echo bleh > bar
hg add bar
hg ci -m 'add bar'

hg cp bar foo
echo >> bar
hg ci -m 'cp bar foo; change bar'

hg debugrename foo
hg debugindex .hg/store/data/bar.i