Fix loading of models in models.py and autodiscovery

[butler]

models are loaded and assigned to lists and dictionaries hard coded in models.py. All that information should now be in the models themselves. Need to replace the huge chunk of code with a loop reading all models in the models directory and getting their names (to populate a model names list for GUI dropdown) and categories and populate the appropriate lists and dictionaries.

Also check to see where autodiscover functionality should be. Can check how is done for custom models currently. Once designed a new ticket should be opened and this one closed… unless the design has the first part of this ticket too intertwined.