Add-Ons loaded per workflow

Memory can be an issue when dealing with large models and it would be useful if the add-ons that you need for one part of your workflow don't have to stay in memory for the entire session.

When enabling an add-on, you could select which workflow layouts this add-on is valid for and the add-ons are loaded when entering this layout.

Of course, you could also select an add-on as "Global" or "All" so it doesn't get unloaded.

Upside: Saving memory as well as not having unneeded tools appearing in tool shelves when not needed.

Downside: Perhaps short delay when changing workflow layouts. Add-ons may not remember preferences or last-used settings when unloaded and re-loaded.