Dynamic maintenance loot table and map modification.

It's kind of an overhaul of the maintenance loot. The loot table is as close to the original item count as i could manage.

I also made a slight modification to the original lootdrop code, spawning items in the constructor (New) rather than initialize() allow them to spawn before lockers and containers are closed, i made it use pickweight() rather than pick(), after reviewing how the pickweight function work, there is no reason not to use it, it's also set to lootdoubles = 1 by default as it's the fastest option.

I replaced the copy pasted "firesuit/hardhat/meson/oxy/gasmask" racks by firefighting lockers.

I also added a couple of extra loot spawning points on empty lockers, and racks (and compensated with more "no loot spawning" chance)

(I'm not responsible for the abundance of gasmasks and fire extinguishers, this is what's currently in maintenance)
What do you mean by "unused"? also /obj/effect/spawner/lootdrop/armory_contraband is a copy i made for the meta armory.