Feature: Event system - Fundamentals

[alex9849]

An UI for the event system has to be implemented.
The user should be able to create new actions by using an "add event"-button.
That button should open a menu where an event and an action can be selected and configured.

Todos:

• Create REST endpoints that handle CRUD-actions for the event system
• Create UI
• Create service and DAO layer for CRUD actions and to trigger events