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)
adding empty-file
adding large-file
adding another-file
removing empty-file
removing large-file
recording removal of large-file as rename to another-file (99% similar)
adding large-file
adding tiny-file
adding small-file
removing large-file
removing tiny-file
recording removal of tiny-file as rename to small-file (82% similar)