Add classid property for <object/> tag

This properties needed to work with ActiveX objects in IE, created by
`<object/>` tag.
Sorry for the *massive* delay.

We can drop this. According to [MSDN](http://msdn.microsoft.com/en-us/library/ie/ms533559%28v=vs.85%29.aspx) this is set via `node.classid`, so we don't need the attribute map (which I think we'll actually ignore since we didn't specify MUST_USE_ATTRIBUTE above.