- Adds client.sync(), which updates all local_db items with the data from pod
- add DB.update(node). Same behaviour as DB.add, but checks instead if item already exists.
- Changed printed errors from DB.add to ValueErrors.
- bugfix: client.add_to_schema no longer adds to local_db. This was storing schema definitions in local_db, which are schemas unknown (and not needed) in pymemri.