Merge Trigger and Scheduler (admin view)

[thorsteneckel]

As discussed and requested by Mark from Locomore:

Currently Schedulers and Triggers are configured in two different admin views. There are some functions missing in the Scheduler view (like e.g. sending mails) that are available for Triggers.

Surely time scheduled tasks and event triggered tasks are two different things - technically. In practice the time component is just another event trigger. This leads to confusion or administrative overhead when the same action should be taken for a Trigger and Scheduler. It's even more confusing when Triggers can take actions that Schedulers can't.

Therefore the proposal is to merge the Scheduler and Trigger admin view to configure a time event as a possible Trigger for actions.

[YetAnotherGerrit]

There is also a FR in the community now:
https://community.zammad.org/t/replace-macros-triggers-and-scheduler-with-a-combined-workflow-system/13495/2