* Mention valid rules and active rules.
* Rename variables accordingly and refactor the trigger related methods.
* Log whether a trigger rule has already been triggered.
* Store change time when loading
* On reload, check if a file exists and whether it is newer
* Fail if the rules file cannot be loaded
* Reload the rules file if the events/scenes file has been reloaded
(This is needed because rules might depend on new or updated
events/scenes)