Add an exit/shutdown method

There should be a way to shut down the context from IJM. I'm not sure if it should actually be in the IJM object or if there should be a more universal method (e.g. static method?) since the IJM instance itself is intended to be just one plugin in a collection of utilities..

Start by locating the IJM object and the context lifecycle it controls. Resolve whether shutdown belongs on IJM or in a universal/static API, then define completion as a callable method that reliably shuts down the context without assuming IJM is the only plugin.

Written by the indexing model from the issue text.