1 Introduction
  
  Erik has had a mental overload and has turned into a vegetable. Fortunately
  an experimental procedure can save his life. In this procedure each of his
  braincells will be investigated and marked as good or bad, after which the
  bad cells are removed using high precision MicroWaves. The removal procedure
  is automatic, but each braincell must be judged by hand.
  
  DrBernard, a well known brain surgeon, will perform this marking task. He will
  use InnerSpace technology to investigate each braincell and judge it. It is
  good that DrBernard has excellent navigation skills, because Eriks brain can
  be a mess at times.
  
2 Assignment

  Implement DrBernards algorithm to navigate Eriks brain and visit and mark all 
  the bad cells. (Marking the good cells is optional :-) Please note that 
  DrBernard needs to visit all the cells from close by, so don't rely on long range
  scanners.
  
3 Example 

  There are 3 brain cells called 'Love','Hate' and 'Sex' and they form a triangle.
  So 'Love' is connected to 'Sex' and 'Hate', 'Sex' is connected to 'Love' and 
  'Hate' etcetera.
  
  DrBernard starts in braincell 'Love' and marks it as good. Then he chooses 
  another cell (at random) and proceeds to 'Sex'. DrBernard also marks this cell
  as good. Then he will proceed to 'Hate' as 'Love' was already marked. DrBernard
  marks this cell as bad. Then there are no more cells to investigate as all cells
  are visited. DrBernard returns from InnerSpace by sending a NULL command.
  
4 Hints

  - Use the MarkerBag to check if you have already visited a cell. 
  - If there are no more cells to visit you're probably done, not ?
  - Use the toString() of BrainCell for a full description.
  - The InnerSpace device has a limited amount of enery. After approx.
    100 moves the safety protocols will kick in.
  