UID MOVE/COPY support

When trying to switch a client to use moveUIDMessages instead of moveMessages, I noticed that the IMAPProtocol still issues a `MOVE` command with sequence numbers to move the messages. Instead, the only difference seems to be the parsing of the COPYUID tagged response.

I had expected it to use the `UID MOVE` command, especially since the moveuid method already depends on both the MOVE and UIDPLUS extensions, and copymoveUIDMessages already fetches UID information for all messages.

The same applies to copyUIDMessages and `UID COPY`, except that it does not rely on the MOVE extension.

The only releated issue I could find is #167. The conversaion seems to imply that the correct way to support this would be new methods (moveMessagesByUID, copyMessagesByUID), which of course would also be fine to keep backwards-compatibility, even though the existing methods seem fitting (from my layman's perspective).

Start with the IMAPProtocol implementation and the existing moveUIDMessages, copyUIDMessages, and copymoveUIDMessages methods. Review issue #167 and verify how UID MOVE and UID COPY should relate to MOVE, COPY, and COPYUID responses; done means the UID-based methods issue the expected UID commands while preserving backwards compatibility.

Written by the indexing model from the issue text.