Adding Refresh menu item for use in case database has changed in the background.
Bug fix.
Cascaded bug: fix
Breaking up table creating into 'meta' and 'cache' types. 'cache' types are inferred from other data. 'meta' are precious user data.
Bug fix: connection was now shared across threads because it was persistent. Solution: create a new Catalog object and create a connection in the thread.
Bug fix: length is not always present in dict.