Implement user_action in waves notebooks #81
Description
Due to time constraints, I wasn't able to get this working during my project. It would be great if the waves notebooks I worked on could have the user_action function implemented so more of the test suite could be run.
It should be achievable by passing save=Nt into the TimeFunction (say, u), and then running user_action on the values in u.data once the Operator has been applied.