Code review comment for lp:~leonardr/launchpad/get-field-uri

This branch adds a new Javascript utility function, get_field_uri(). This function lets you get the URI to a field resource, given an entry resource and a field name.

In addition to unit tests of the new function, this branch adds two tests that make sure patch() works on a field resource.

This branch also gets rid of the client_parse_xml_entry method, which is not used within Launchpad and which was a bad idea in the first place.

You'll get one Javascript failure when running the Windmill tests, but that's a failure currently in trunk; it's not introduced by this branch.