help: Update several pages of the help manual
- Change mentions of the "Alarm" tab to "Alarms"
- On the "Add an Alarm" page, reorder the items to match the order of the controls. Also, clarify that you can select no weekdays if you want the alarm to only go off once.
- On the "Edit an alarm" page, split the information about disabling an alarm into a new section, since that is not done through the Edit dialog anymore. Also clarify how to edit an alarm, since you now need to press the Edit button rather than the whole row.
- Update several button names on the stopwatch page