Suit collars

Adds a collar overlay above the helmet layer if the suit has one
The suit needs an identically named sprite in icons/mob/collar.dmi that just contains the part of the suit you want overlayed
~~Suit also needs 'collar = 1' set in utility.dm~~ No coding required by spriters!

Trenchcoats are go!

Note: initial commit includes collar for Susan's new sec bomb suit sprites - #4362