Fixed accessories becoming improperly detached...

when the host suit was clicked on. It is also now clearer who has the
responsibility for attaching and removing accessories.
Accessories are now visible when attached

Uses overlays.

I was originally planning to use the SOUTH direction of the
icons/mob/ties.dmi image as the overlay, however this had problems with
the fact that those images are directional. Rather than override Move()
in clothing/under to reset dir to SOUTH whenever clothing with an
attached accessory was thrown or dragged, I thought it would be less
hacky to read the overlays from a separate .dmi.
Merge pull request #4963 from mwerezak/accessory-fix

Accessories