Includes antag HUDs in the datum hud overhaul

Makes hud_list associative, and introduces the /atom list hud_possible,
which lists all the possible hud images a certain atom can provide.

Replaces all the awful procs in the gamemodes with their new
/datum/atom_hud versions, which are much shorter, simpler and faster.

code/modules/admin/verbs/one_click_antag.dm

@@ -302,8 +302,6 @@ client/proc/one_click_antag()
 				new_character.mind.make_Nuke(synd_spawn[spawnpos],nuke_code)
 			spawnpos++
 
-		ticker.mode.update_all_synd_icons()
-
 	return 1