ITS tagset draft: Section by Christian

Hi all,

I integrated the new version of section 3.1. from Christian into the
working draft. I think it gives a very good 0therview of ITS in general,
so I thought of putting it into a separate main section. (I have not
asked Christian about this position change though, Christian, all, what
do you think?). Please have a look at
http://www.w3.org/International/its/itstagset/itstagset.html#sel-intro-expr
and comment.

Regards, Felix.