Finish http refactoring. Test suite passing.
* bzrlib/transport/http/_urllib.py:
(HttpTransport_urllib.__init__): Simplified.
(HttpTransport_urllib._remote_path): New method. Get rid of
authinfo only for urllib2 purposes.
(HttpTransport_urllib._perform): Rewrite the connection sync
between transport and request.
(HttpTransport_urllib._get, HttpTransport_urllib._get,
HttpTransport_urllib._post): Updated for the new connection handling.
* bzrlib/transport/http/_pycurl.py:
(PyCurlTransport.__init__): Simplified.
(PyCurlTransport._get_curl): New method.
(PyCurlTransport.has, PyCurlTransport._get_full)
(PyCurlTransport._get_ranged, PyCurlTransport._post): Use _get_curl().