More footer fixes

In the new Dryad footer, I've changed some link text (to 'Dryad Terms of Use') and given it a proper destination.

As suggested in the Issues document, I've also changed the __Contact Us__ link to point directly to ```/feedback```.

NOTE that the feedback page is broken on the staging server (throws an ```AuthorizeException```). This happens whether we get there from the footer link or the main menu above.