Porting contained sprites and first custom item wave (#484)

Porting the contained sprite var from old code, allowing for less problems with icon storages in the future.

Custom items added:

Antique Pocket Watch - Eric Derringer - xelnagahunter
Mendoza's cap - Chance Mendoza - loow
Ziva's Bandana - Ziva Ta'Kim - sierrakomodo
Fancy Jacket - Zubari Akenzua - filthyfrankster (req_titles: Security Officer, Warden, Head of Security, Detective, Forensic Technician)
Heirloom Unathi Mantle - Sslazhir Yinzr - alberyk
Chich Eyewear - Roxy Wallace - nebulaflare
Data Chip - Roxy Wallace - nebulaflare
Sharpshooter Gloves - Hawk Silverstone - nebulaflare
Data Drive Pendant - Kyyir'ry'avii Mo'Taki - nebulaflare
Graphite's chassis - Grap..Null - dreamixpl
Skrell Purple Head Cloth - Shkor-Dyet Dom'Pesh - mofo1995
Pocket Altar - Kiara Branwen - nursiekitty
Brown Hat - Avery Bell - serveris6
Pinned Brown Coat - Avery Bell - serveris6

Also, adding old custom synth sprites from old code.

code/game/objects/items.dm

@@ -41,7 +41,8 @@
 	var/obj/item/device/uplink/hidden/hidden_uplink = null // All items can have an uplink hidden inside, just remember to add the triggers.
 	var/zoomdevicename = null //name used for message when binoculars/scope is used
 	var/zoom = 0 //1 if item is actively being used to zoom. For scoped guns and binoculars.
-
+	var/contained_sprite = 0 //1 if item_state, lefthand, righthand, and worn sprite are all in one dmi
+	
 	var/item_state = null // Used to specify the item state for the on-mob overlays.
 	var/item_state_slots = null //overrides the default item_state for particular slots.