[mapistore-python][sample-backend]: implement delete_message (hard deletion)
[mapistore-python][sample-backend]: enable get and set properties for attachments
[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]: Correct white spaces and blank lines
[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 move and copy folder
[mapistore-python][sample.py]: Use list and dictionary operations instead of for loops
remove destructors
[mapistore-python][sample.py]: Correct for loops (esp. naming)
[mapistore-python][sample.py: Enforce property usage instead of FID/MID attributes
[mapistore-python][sample.py]: Add breaks (only one message/attachment with the same ID can exist in the "message"/"attachment" list)