Welcome to the elevater control Kata!

The elevators computersystem has recently crashed and deleted the whole control
implementation. All thats left are two interfaces, to see, how the control
should be.

Your task is now to implement a working ElevatorController implementation,
that fullfills the following kriteria.

- The elevator can be called from every level of the building (-2,-1,0,1,2,3,4,5,6)
- The elevator can recieve assignments for every level of the building
- In case of an emergency (e.g. fire) the elevator is instantly heading to
  groundlevel (0) and is ignoring further calls or assignments until an emergency reset.
- The elevator stops at calls which are on his way
- The elevator stops on every assigned level in the correct order (numerical)