[PATCH 0 of 2] Optionally display chains of empty directories in hgweb manifest view

[Ry4an Brase]

When a manifest has a series of directories with nothing in them but a
single directory, displaying the entire chain of empty directories
allows for navigation down to the first non-empty directory with a
single click.

This behavior is disabled by default (both display and detection), can
be enabled in the [web] section, and uses the template system.  Because
Java links package hierarchy to directory hieracy, and because Java
conventions include at least three empty directories at the top of this
hierachy, this decending of empty directories is par for the course in
Java web tools.

For this manifest:

    a1/a2/a3/a4/a5/file1
    a1/a2/b3/a4/a5/file2
    b1/b2/b3/b4/b5/file3

the resulting view in the paper theme is:

    http://ry4an.org/tmp/mercurial-paper-decend-empties.png