[sample.py]: Fix typos
[mapistore-python][sample-backend]: enable get and set properties for attachments
[mapistore-python][sample-backend]: fix set_properties and save (changes in folders and messages didn't have any effect)
[mapistore-python][sample-backend]: implement delete_message (hard deletion)
[mapistore-python][sample-backend]: fix attachment ID behaviour, use attachment cache and add set_properties
[mapistore-python][sample.py]: include "next_aid" in message entries
[mapistore-python][sample-backend]: implement create_attachment
[mapistore-python][sample.py]: fix white spaces and line breaks
[pymapistore]: include attachment ID in Python bindings
[python-backend][sample.py]: Rename "message"/"attachment" dictionaries as "basedict" (+clarity and consistency with folder class)
[mapistore-python][sample.py]: Don't remove message from the cache when saving it
[python-backend][sample.py]: add destructor so objects in the cache are cleaned
[mapistore-python]: implement ROPSaveChangesAttachment
[mapistore-python][sample.py]: Implement RopGetValidAttachments in OpenChange
[pymapistore]: Modify "attachments" iterator to fit the attachment ID behaviour
[mapistore-python][sample-backend]: Implement move_copy_messages
[mapistore-python][sample-backend]: implement delete_message (hard deletion)
[mapistore-python][sample-backend]: Implement move and copy folder
[mapistore-python][sample.py]: Use list and dictionary operations instead of for loops
[mapistore-python][sample.py]: Correct for loops (esp. naming)