Sandbox improvements
Reduced the overwhelming size of items list by removing huge categories into their own separate lists; this affects /obj/item/clothing and /obj/item/weapon/reagent_containers.
Removes a bunch of unsanitary items from the spawn list.
Makes RCD quick spawn button check for spawn disabled flag since it can destroy walls and floors with impunity.
Adds cleanbot to quick spawn list.
Removes the check for the spawn flag from the dialog construction, because it is cached; if the admin turns it on during the round, people who already have a sandbox panel will be unable to use it.
Adds a disclaimer to the sandbox panel vis a vis admin disabling.