RDF*: Quad#equals missing Term type

[rubensworks]

It should be allowed to pass a Term to Quad#equals given our recent RDF* changes. Right now, only Quad is allowed to be passed.

[blake-regalia]

Also, fromQuad is now obsolete. Another also, would be good to mention in the spec that Quad#value can be ignored when testing Quad#equals since this should be guaranteed constant empty string if .termType test passes.

Also, fromQuad is now obsolete. Another also, would be good to mention in the spec that Quad#value can be ignored when testing Quad#equals since this should be guaranteed constant empty string if .termType test passes.