templating comparison update

I've made some updates to the templating comparison at
http://perl.apache.org/docs/tutorials/tmpl/comparison/compar ison.html.

- Removed outdated Apache::AxKit information and replaced it with a
brief description of AxKit2.

- Improved coverage of Petal and added Template::TAL.

- Fixed typos pointed out by Fred Steinberg
and Charlie Harvey .

The next update will be to add Template::Alloy.

- Perrin