Allows dev and testing/debugging to focus on one (shape or behavior) without getting mixed up in the other, will also enable different portal shapes later on. Other adjustments:
* Reuse/reignite an existing portal or portal frame if there is one at the remote destination, rather than the area being overwritten by a slightly offset portal schematic.
* Create remote portals in a matching orientation to the local portal.
* Preserve player position & facing relative to portal when traveling through wormhole (even if portals are at 90°)
* Players no longer bounce several times after teleporting
* Player is not teleported until after the portal at the other end is confirmed/built
32affba6 re-registered stairs which have already been registered 20 lines earlier in the code, and registered them as "brick" causing the netherbrick stairs to replace Minetest's default:brick stairs. The rest of 32affba6 was already unrolled in 7a0e52da, but the stairs bug remained.
Reuse a single table for content ids to reduce memory use.
Add DEBUG parameter to control printing of mapchunk generation time,
set to false as default.
Add missing noise parameters (parameters are default and unchanged).
Large caverns using squashed 3D noise
Less lava, more glowstone, no air pockets
Preserve nether dungeons
Allow light to spread from glowstone and make brighter
Fix 'is ground content' settings, portals should not be
excavated by overgenerated caves
Rack drops itself as normal
Make brick, fence, stair, slab groups consistent
Use 'node sound gravel defaults' for sand
Make brick crafting consistent with default
Make fence recipe output number consistent with default
Make 'emerge area' volume mimimum required size
Add 'find nether target y' function to search for a cavern
floor with space above for nether portal spawn
