Compare mob facing helper proc [Review and discuss before merge]

This new proc compares the direction two mobs are facing when it is called, giving unique returns if the mobs are facing the same direction, facing opposite directions, or one facing perpendicular to the other. 

This proc would allow adding unique effects on interact on facing, such as giving a higher chance to stun if you target the head and hit someone from behind with a toolbox, or a higher chance of blinding someone with a laser pointer if the two mobs are facing one another.

I have not implemented a current use for this proc yet, nor have I extensively tested it's function.

I do need feedback on my exclusion if statement, because I feel I may have been excessive in what is being checked for.