Additional Structures

+ 5 new underground structures (underground base, underground prison, sewage system, underground stollen, underground village)

+ 8 normal structures (fallen dead trees, fallen palms, nether totems, nether fire)

+ ingame config! (please delete the old config file!)

+ random spawn height of underground and flying structures

+ support for all 1.12 versions

* structure generator rewrite

* 6 improved structures

* foundation generator now replaces grass, fern and double plants too

* foundation generator generates the foundation sometimes in the wrong direction is now fixed (wip)

* "flying" structures fixed

* structure spawn on odd places in the many cases fixed

* ground "eating" through big structures fixed