Slugifying news and events urls

PFA two patches that do this.

AFAIK that gives for better SEO as well, but in general it just makes
things look nicer :)

We already had support for the <id>-<slug>/ format URLs, but we never
generated them. But for things to look nicer, this patch instead uses
<slug>-<id>/.

Old URLs still work, and if the title (and thus slug) is changed it will
redirect to the new location, to maximize future caching for it.

For news, it adds the slugified url to the admin list, primarily to make it
easier for the person who's doing a "web release" to be able to copy/paste
the actual complete URL instead of having to rely on trying to figure out
what slugify does.

Thoughts? And for those who actually know Web Stuff (TM), is it correct
that this should also help with SEO stuff?

--
Magnus Hagander
Me: https://www.hagander.net/ <http://www.hagander.net/>
Work: https://www.redpill-linpro.com/ <http://www.redpill-linpro.com/>