Tarball, etc, links need updating in templates

[Bryan O'Sullivan]

I hardly use hgweb at all, but when I went to point someone at the
autogenerated tarballs for changesets I found them hard to find.  A
two-letter "gz" link is not very descriptive.

If someone would care to send in a patch that changes "gz" into
"tarball", it would be useful.  A further very useful patch would be
tooltips for the cryptic links across the top of a page.

	<b