Notifications & code cleanup

Mainly addressing TODO items, so we no longer send group and name in notification responses, update
the test suites to do the same, etc.
All demonstrations are working with current API, GTK demo fixed up, and we now use a `_cleanup_key_` helper as previously discussed to make life easier for managing BuxtonKey's.

My rationale here is not manually tracking the free's, and especially when we encounter multiple cases where a return could happen in a function, just bloats code having to call free from multiple points.