Loot rebalance

Adjusts the material ranges of generated items to be more in line with the level range of the zone. Overall this makes each tier of loot appear a little later in the game, so it spreads the loot progression better. Items generated in vaults are allowed to be 1 tier higher than the rest of the zone is allowed to drop, making vaults more rewarding. The final level of Vor Armoury generates its loot as a vault, so it should still contain t5 some items. Each time the shops restock they should have their material range increased by 1.

I haven't specifically tested that shops tier up or that Vor Armoury does drop t5 loot, but the increased tier of loot in vaults works. Likely needs playtesting and tweaking.