deleteAll method
Deletes the store if a store is implemented in a way that puts all the named stashes in one storage, or stores(s) if multiple storages are used
Implementation
Future<void> deleteAll() {
return Future.wait(_partitions.keys.map((name) {
return _db
.close()
.then((_) => deleteDatabase(_db.path))
.then((_) => _partitions.remove(name));
}));
}