Add last_login field to auth.txt

Also shortens some related code and adds more parameters to string.split.
Fix dump() indentation with non-tab indents
Speed up removing a node (less block mesh updates).
Add mgv5. New noise code, uses biome API. Eased 3d noise for terrain, caves, blobs
Fix regressions and minor improvements in refactor_the_game
a) Fix double tap for jump and show_debug
b) Revert changes to limitFps()... there is no verification that the new method was an issue, but going back to old method just in case
b.2) limitFps() no longer calls device->run() and also no longer has to be called immediately after a call to device->run()
Stop inserting empty lines at end of minetest.conf file each time it is rewritten

See: https://github.com/minetest/minetest/issues/1790
Implement WieldMeshSceneNode which improves wield mesh rendering

- Don't create and cache an extruded mesh for every (non-node) item.
  Instead use a single one per image resolution.

- For cubic nodes reuse a single wield mesh too

- Improve lighting of the wielded item

- Increase far value of wield mesh scene camera, fixes #1770

- Also includes some minor refactorings of Camera and GenericCAO.
Merge remote-tracking branch 'minetest/master'

Conflicts:
	build/android/jni/Android.mk
	builtin/game/auth.lua
	builtin/game/chatcommands.lua
	builtin/mainmenu/dlg_create_world.lua
	freeminer.conf.example
	src/camera.cpp
	src/camera.h
	src/client.cpp
	src/content_cao.cpp
	src/environment.cpp
	src/game.cpp
	src/itemdef.cpp
	src/mapgen_v5.cpp
	src/mapgen_v5.h
	src/noise.cpp
	src/util/numeric.h