Path and angle tweaks

- The angle method in vector now presumes that the origin of the coordinate system is in the top left rather than in the bottom left
- ShortestPath now uses a queue (LinkedList) and pushes elements at the head of the queue rather than pushing things on top of a Stack and reversing it afterwards
- Found out that it didn't have any impact on the angle calculations wether the edges returned by ShortestPath are actually pointing in the right direction (the confusion was due to the the angle method presuming origin in bottom left corner)