DSigProposal references

Hello Patrick

Further to this afternoon's discussion I have added references to the
ETSI XAdES standard and the W3C XML-DSIG (courtesy of Dennis).  You
can check what I have here:
http://wiki.oasis-open.org/office/DSigProposal.

I'm also not sure about the URI to one-hop-from-what-you-really-want.
I've fudged by saying "available via http://.." instead of "available
at".  Feels a bit like cheating, but this is the reference the ETSI TC
gave us.  It looks like you can bypass the whole rigmarole and go
straight to http://pda.etsi.org/exchangefolder/ts_101903v010302p.pdf
but perhaps they want readers to read the copyright notice and the
blurb first.

Cheers
Bob