in order to be able to run sql/models.py alone (e.g. sphinx autodoc)
- Made the storage model slightly more flexible - Made a small P-o-C GUI application in GTK - Polished accounting.client - models.Transaction.id is now a str - Fixed transaction.id marshalling for storage.ledgercli
- Added Storage ABC - Moved Ledger class to storage/ledgercli.py - Added SQL requirements to requirements.txt