change engine timers when rule intervals change

[Nasdneb]

The engine has it's own timers, that are scheduled according to the intervals of the rules. Now when a change of these intervals in the rules happen, the engine should change it's timers to the new intervals

[serapath]

Added to SPECIFICATION/README.md in upcoming pull request -> please discuss it there.

I recommend to CLOSE this issue, @Nasdneb

UPDATE:
The latest updates are to be found here: #9