Suggestion: Event Controller: Different Thresholds for Enable/Disable

A common use case for the new Event Controller block is to enable (or disable) a process that counteracts the observed value, and disable (or enable) that process again once the value is back within acceptable limits; e.g.:

- Disable a drill rig if the associated storage container is about to exceed a particular threshold, and re-enable it once there is capacity again.

- Enable a Filter pushing a certain ore into a Refinery if a storage container for the associated ingots drops below a certain threshold.

However, in many such cases, achieving this with a single Event Controller using both its "on" and "off" actions will result in the respective process to rapidly "flutter" between the active and inactive state, which is often undesired (if only because it might be accompanied by annoying sound).

To avoid this, currently two Event Controller blocks are needed: One to turn the process on once an upper threshold is reached, and one to turn the process back off once a lower threshold is reached.

I hereby propose to add a dedicated secondary threshold to the Event Controller:

- Once the observed value is >= (or <=) the specified "on" threshold, the "on" action is performed until further notice.

- Once the observed value is <= (or >=) the specified "off" threshold, the "off" action is performed until further notice.