Fix issue with dropdown menu
Update main template to include more editable fields
Fix number alignment
Refactor and redesign context menus

Instead of having inline popups for editing/removing sentence elements,
all editing actions have been moved into a context menu that appears
when any sentence element is clicked. The context menus have also been
refactored and redesigned to work with any element.
Re-add element removal for sentences
Add placeholders for adding new sections