Adds some missing drone things from the previous PR/new drone things

Missing drone things: 
+Missing head/mask slot because drones.dm is not currently being compiled
 +Missing weapon/storage not allowing drones to MouseDrop
 +Missing uplink buy() preventing non-humans to use it
 +Missing syndrone sprites

New drone things:
 +Drone pings respect factions
 +Moved drone ping message functionality into its own proc
 +Alerts all drones about newly activated/reactivated drones
 +Alerts all drones about dead drones
 +Gives the syndrone the "syndicate" faction, overriding the default "neutral"
 ->Redirected gib() to dust()
 ->Redirected update_inv_l_hand() to update_inv_hands()
 ->Redirected update_inv_r_hand() to update_inv_hands()
 ->Redirected update_inv_wear_mask() to update_inv_head()