blackbox: properly replace ui class Without this, anyone creating a ui object using: uimod.ui() skips the blackbox. Also, anyone doing ui.copy() skipped the blackbox. Unfortunately, the ui object lifestyle is a bit messy, the first one that's created is never actually initialized with subclasses, instead pieces of the subclass are adopted into the primal ui object. In order to handle this, a _partialinit method will be called to ensure that the blackboxui is properly initialized.