Rename to Luanti (#15294)

The new header intentionally isn't in MTG stone design (or any other MTG-esque design), since we want to distance Luanti and MTG from each other. The font "undefined medium" (https://undefined-medium.com/) was used. 

ASCII art generated by https://patorjk.com/software/taag/#p=display&f=Graffiti&t=luanti
https://github.com/minetest/minetest/pull/11952#issuecomment-1013364703

---------

Co-authored-by: sfan5 <sfan5@live.de>

doc/luanti.6

@@ -1,26 +1,21 @@
-.TH minetest 6 "2 February 2019" "" ""
+.TH luanti 6 "2 February 2019" "" ""
 
 .SH NAME
-minetest, minetestserver \- Multiplayer infinite-world block sandbox
+luanti, luantiserver \- voxel game engine
 
 .SH SYNOPSIS
-.B minetest
+.B luanti
 [\fB--server SERVER OPTIONS\fR | \fBCLIENT OPTIONS\fR]
 [\fBCOMMON OPTIONS\fR]
 [\fBWORLD PATH\fR]
 
-.B minetestserver
+.B luantiserver
 [\fBSERVER OPTIONS\fR]
 [\fBCOMMON OPTIONS\fR]
 [\fBWORLD PATH\fR]
 
 .SH DESCRIPTION
-.B Minetest is one of the first InfiniMiner/Minecraft(/whatever) inspired games
-(started October 2010), with a goal of taking the survival multiplayer gameplay
-in a slightly different direction.
-.PP
-The main design philosophy is to keep it technically simple, stable and
-portable. It will be kept lightweight enough to run on fairly old hardware.
+.B Luanti (formerly Minetest) is a voxel game engine with easy modding and game creation.
 
 .SH COMMON OPTIONS
 .TP
@@ -126,7 +121,7 @@ Colon delimited list of directories to search for games.
 Colon delimited list of directories to search for mods.
 .TP
 .B MINETEST_USER_PATH
-Path to Minetest user data directory.
+Path to Luanti user data directory.
 
 .SH BUGS
 Please report all bugs at https://github.com/minetest/minetest/issues.

doc/luantiserver.6

@@ -0,0 +1,2 @@
+.so man6/luanti.6
+

doc/minetestserver.6

@@ -1,2 +0,0 @@
-.so man6/minetest.6
-

doc/mkdocs/docs/img/favicon.ico

@@ -1 +1 @@
-../../../../misc/minetest-icon.ico
+../../../../misc/luanti-icon.ico