wiki updates

FYI, I've added more content and structure to the proposal section of 
the wiki.

	<http://wiki.oasis-open.org/office/metadata_proposal>

I included a current draft RELAX NG schema for the metadata model and 
syntax, and suggest we might start with this and at least settle on a 
general approach that we can always tweak later.

I've also identified three other separate areas of work:

    	Associating Metadata with Document Content
    	Metadata Extension Modules
    	Identifying Document Fragments and Metadata Collections

Bruce