Treatment of GRAINBOUNDARY approach
The equilibrium distance when approaching a GRAINBOUNDARY is set.
Moved distance check out of switch
The checking for the distance is the same for all defect cases. This is
thus moved out of the switch.
Added equlibrium position for FREESURFACE
The FREESURFACE is supposed to be a sink for dislocations. So ideally
the dislocation can go into it.
Moved the distance checking outside the entire block for checking
collisions.