Annotations draft updated

[James Clark <jjc@jclark.com>]

I've updated my annotations draft based on the discussions with Murata-san:

http://www.thaiopensource.com/relaxng/annotate.html
http://www.thaiopensource.com/relaxng/annotate.xml

Specifically,

- I changed the title
- I greatly expanded the introduction
- I avoided any implication that the spec must be implemented by a RELAX NG
validator
- I strengthened the restrictions on using name classes in conjunction with
the annotations
- I generalized the Level 2 conformance requirements to allow implementation
without any actual infoset modification
- I mentioned that the a:documentation annotation corresponds to XML 1.0 DTD
comments
- I mentioned xml:lang.
- I said explicitly say multiple child a:documentation elements are allowed.
- I added a new section with an example.

James