Undo/Redo Behavior Sometimes Unclear

[spencerw]

Performing actions with certain gadgets triggers a chain of state changes, which are not always obvious to the user. For example, loading a data set with the data inquirer saves the input text and then loads the data set, which are two separate state changes. If the user wanted to undo their text entry, they would have to click undo twice, even though they only performed one action.

We should add a panel which displays the history of state changes. This way, it is more obvious what happens when the user clicks undo/redo.