* Added: support IMAP command MOVE at BaseMailBox.move
* Added: MailboxMoveError, raises from BaseMailBox.move when MOVE command is supported
* Added: chunks argument for BaseMailBox.(copy,move,flag,delete) methods - Number of UIDs to proc at once, to avoid server errors on large set
* Changed: BaseMailBox.(copy,move,flag,delete) result types
* Changed: utils.clean_uids now returns List[str]
* Changed: utils.chunks_crop -> utils.chunked_crop, n arg renamed to chunk_size and it takes False-like vals
* Renamed: utils.chunks -> utils.chunked