Fix copying of terms.

When creating the copy button, there was apparently one case we missed:
trying to cop terms from pages such as http://xmlns.com/foaf/0.1/ only copies the namespace.
The expected behavior would be to copy the whole URL of the term.

This pull request should fix this. (But please test.)

PS I couldn't simply extend the range of the `<span class="uri copy">`,
because the voting script relies on `.uri` being the namespace.