Fix StackEditFragment by changing superclass to Fragment (was ListFragment)

- The only reason this had a `ListView` was because it was going to have user added dates, but this won't be in MVP.
- I took out the adapter in one of the last few commits (today) so the listview wasn't showing anything (previously, it showed EditTexts in the listView header).
- In this commit, I changed the superclass to Fragment (no need for ListView anymore) and set the layout to what was previously the listview header.