Correct fast tag selection: expert is a symbol.
Several small fixes:

- Don't log changes to repeating tasks (seems pointless)
- After exporting agendas and iCalendar, return to the window state (if it
  changed)
- Export iCalendar timestamps if active only, with 15 minute alarm
- Redo agenda buffer once changing a recurring event
- Save org buffers after changing state.
Add comment to variable.