Rework getClosestMine to check across the edge of the screen

[se-ke]

Currently, getClosestMine works by checking the distance between each agent and each mine as if they were on a flat surface, a rectangle. However, the edges of the rectangle are in fact linked together to form a torus. So, if an agent is on the left side of the screen, it will not determine that a mine on the right side of the screen is closest to it because it does not account for the edges being connected. This could be fixed by testing multiple location of the mine (ex. (x,y), (x-width, y), (x, y-height), (x-width, y-height), (x+width, y), (x, y+height), (x+width,y+height)), but this is rather burdensome.