Thoughts on planner-notes

Actually, subcategories are already handled by separate plan pages, so
I don’t need subtopics any more. I would, however, like to see all the
note headlines, possibly bounded by certain dates. That would be fun.
In which case, I don’t need to merge anything in from planner-notes –
I can just work with the export functions I already have in
planner-experimental.

../../notebook/emacs/emacs-wiki/planner-notes.el