[Behavior] Grid move: add "Action:Approach/Depart"
This action will let the chess move to neighbor to approach to target by shortest physical distance, or depart fro, target by longest physical distance.
It's another way to do approaching. (One way is using path finding.
But, the chess will be stuck in some cases like
<img src="http://i1081.photobucket.com/albums/j352/rexrainbow1/stuck_zps58e384f1.png" border="0">
The green chess will stay at that cell which has (local) shortest physical distance to target (black chess).
The path finding is smarter then "action:approach".