QWebFrame::url() does not return a valid URL for iframes. We can't just
look up the requested URL in m_responses because the request may have
been redirected, so instead we keep track of redirects and set up the
NetworkResponse when the final reply is received.
Adds a SetBlacklist command that takes a list of URLs
which will be black listed by the WebKit Server. When
a request is made to one these URLs webkit_server will
intercept the request and return a NoOpReply which contains
no content.