Re: [libvirt] Re-write the domain XML reference docs

The current domain XML format documentation reference on the website is very out of date and not well structured since we organically added random bits to it as we wrote drivers. This patch is starting from a clean slate. I've removed all existing content and have written a clear & concise reference for (all?) XML elements we support in the domain XML format. This is following the style I've used for the storage and network XML format docs. Basically I've grouped the difference elements into logically related sets and then described each one, giving examples and details of all attributes they support. This also covers the new serial/paralle device syntax I added recently. The example configs for Xen, QEMU, etc domains are all in the driver specific docs already, and linked at the bottom of this page. The patch isn't particularly nice to review, so I'd recommend applying it and looking at the resulting 'formatdomain.html' page in your web browser