webdav: implement COPY and MOVE.

Also add a -port flag to litmus_test_server.

13 of 13 copymove tests from the litmus suite pass, as does 16 of 16
basic tests.

Change-Id: Idf92cad281e15db7d4d62e28e366ea7bfa89e564
Reviewed-on: https://go-review.googlesource.com/3470
Reviewed-by: Nick Cooper <nmvc@google.com>
Reviewed-by: Robert Stepanek <robert.stepanek@gmail.com>
Reviewed-by: Nigel Tao <nigeltao@golang.org>
4 files changed