[mapistore-python][sample.py]: Add breaks (only one message/attachment with the same ID can exist in the "message"/"attachment" list)
[mapistore-python][sample.py]: Return MAPIStore errors instead of magic values

- Not necessarily a permanent solution - the MAPIStore Python bindings might stop being exposed in the backend at some point
[mapistore-python]: implement ROPSaveChangesAttachment
[mapistore-python][sample-backend]: Implement move and copy folder
[move-copy]: Outline of the move_folder, copy_folder and move_coopy_messages operation
[move-copy]: Extend the implementation of copy_messages
[move-copy]: Extend the implementation of copy_folder