[Feature] introduce tasks into Raa

This MR introduces the Tasks into the Raa-class that existed from prior work from @fbock et.al It does not change code structure but adapts the implementation to some new aspects of the code (e.g. namespaces). Most of the introduction was more or less copy/pasting of the code into the right place.

EventDisplay and Calculator were more complicated and maybe incorrect! I especially created separate commits for them to allow easier code review (now and later).

Implements #13 (closed)