#347 Fixed infinite loop when dragging a node over the central node. In the last commit I actually detected a code smell that was causing this problem. I have fixed up the node highlighting function. I need to go over the link highlighting function as well, and check other related bits for further code smells. I have used my adjacent linsk method rather than trying to detect nodes and edge relations on the basis of their coordinates, which was an approach pasted from the very original D3 example, if I recall.