We can now show replay buttons for the audio contained in {{FrontSide}}
without having to play it again when the answer is shown.
The template code now always defers FrontSide rendering, as it wasn't
a big saving, and meant the logic had to be implemented twice.
This allows us to add a docstring to .append() so users can see
the names of the arguments that are being passed, and means we
don't have to remember to prepend run_ when calling a hook.
Still todo:
- Add separate module for GUI hooks
- Update the remaining runHook/runFilter() calls
- Document the changes, including defensive registration
