Remove /XRD/Link/Property

[Toby Inkster <mail@tobyinkster.co.uk>]

<Property> as a child of <Link> seems to be an unnecessary complication.
The main use case as I see for it is specifying the versions of some
protocol that an endpoint supports. i.e.

	<Link rel="http://example.net/webcam-protocol";
		href="/my-webcam">
		<Property type="http://example.net/webcam-protocol/version";>1.0</Property>
		<Property type="http://example.net/webcam-protocol/version";>2.0</Property>
	</Link>

I don't think <Property> is really needed here. Once version 1.0 of the
protocol is published, links can just use:

	<Link rel="http://example.net/webcam-protocol"; href="/my-webcam" />

If a version 2.0 of the protocol is published offering improvements over
version 1.0, it may have been designed so that 2.0 clients don't need
prior knowledge of the protocol version supported by the endpoint, in
which case, version 2.0 can continue to use:

	<Link rel="http://example.net/webcam-protocol"; href="/my-webcam" />

However, if an explicit version indicator is needed to help version 2.0
clients:

	<Link rel="http://example.net/webcam-protocol"; href="/my-webcam" />
	<Link rel="http://example.net/webcam-protocol-2"; href="/my-webcam" />

And to cover the final possibility, if version 2.0 is completely
incompatible with version 1.0, then the XRD would just contain:

	<Link rel="http://example.net/webcam-protocol-2"; href="/my-webcam" />

So that version 1.0 clients won't inadvertantly follow the link.

I'm not suggesting the removal of the <Property> element altogether -
just disallowing it as a child of <Link>. It would still be allowed as a
child of <XRD>.

Removing it simplifies parsing XRD files, simplifies the data structure
and would probably ease XRD publisher confusion given that right now
<Property> can occur in two places, with different interpretations.

-- 
Toby A Inkster
<mailto:mail@tobyinkster.co.uk>
<http://tobyinkster.co.uk>