'owner' is no longer tracked by the MetaDB

The data source can configure how schemas are used.

If they supply a value for the 'owner' attribute/method, then only that one schema will be searched during 'ur update classes', and class table_names will be simple table names.

If 'owner' is a false value, then all schemas will be searched during 'ur update classes' and table_names in class definitions will be qualified names like schema.table.

This fixes AR747 by not crashing with the given command line.  'ur update classes' is still having problems running on the whole of GMSchema, but I can make a separate branch for those fixes.

This pull request supercedes the prior one.