Adds a magma oceans region to the nether outside the existing nether caverns, which can be reached via tunnels.
Other misc changes:
* chatcomment nether_whereami, a debug aid for knowing which perlin-noise region you are in
* Nether ores no longer obtainable on the ceiling
* Move crafts into crafts.lua
* Add steam to lava cooling, and play bubbling lava upon death by lava
* Add cracked netherbrick
a decorative node which can only be obtained from dungeons or structures
I encourage someone to improve or replace the cracked netherbrick texture. For copyright purposes it's currently a derivative work (by me, 2020) from nether_brick.png, which is licensed under CC BY-SA 3.0 by PilzAdam, so it can fall under the "All other media" PilzAdam's credit in readme.md rather than need its own entry.
* respect protected areas when spawning remote portals
* Use portal_shape to determine area to check for natural/protected
* Log warning on deprecated function call
Prevents the c++/native mapgen from placing ores or decorations (when useBiomes is true).
The biomes-based implementation is faster, more deterministic, and keeps its dungeons, but requires MT 5.1 features to work.
Also
* Glowstone & Netherrack stalactites
* Include the new decorations in mapgen_nobiomes
* Decorate dungeons - Add windows and glowstone "chandeliers" to some rooms
* Configurable Nether floor and ceiling depths
