Improve junk items variety in southern stashes

[oleh5230]

In brief, puts most basic materials in 1st tier and most junk items in 2nd tier to improve variety (currently almost every Cordon stash drops a mirror or a jar, for example).

Also assigns tier 6 to Gauss ammo, should make them as rare as other best AP ammo I think.

[Grokitach]

But then north / middle stashes spawn what...?

[oleh5230]

Sorry, wanted to test this more before responding but I don't have much free time lately.

So far high tier stashes seem to just not spawn junk, which is reasonable I suppose. But I will take some more time on stash changes.