This patch adds two new functions to the event base to allow deprecation of
the individual events, without entirely removing them from the UI.
This is different to our normal deprecation procedure because all events
must support display of historical data. It must also be possible to view
the event information in the event monitor.
When the rule plugin is not a module you can subscribe
to it without having to select to which module instance
you want to subscribe, so there is no need to display
a drop down menu.
