Comments: Inverted Z axis.

-Comments fix, No code has been changed.
-Inverted the Z axis in the comments and changed all dependent comments accordingly.
-Added NORTH/SOUTH/EAST/WEST in addition to LEFT/RIGHT/UP/DOWN.
Uppercased Z

Minor, no code changed.
Merge pull request #870 from wiseoldman95/patch-1

Comments: Inverted Z axis.