[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]: add destructor so objects in the cache are cleaned
[mapistore-python]: implement ROPSaveChangesAttachment
[mapistore-python][sample.py]: Implement RopGetValidAttachments in OpenChange
[sample.py]: Fix typos
[pymapistore]: Modify "attachments" iterator to fit the attachment ID behaviour