ISO fixes: rename liveuser->antergos, add Antergos NeXT os-release, drop lsb-release, fix wallpaper/Plasma setup

airootfs/etc/group

@@ -1,8 +1,8 @@
 root:x:0:root
-adm:x:4:liveuser
-wheel:x:10:liveuser
-uucp:x:14:liveuser
-nopasswdlogin:x:966:liveuser
-rfkill:x:983:liveuser
-sys:x:3:bin,liveuser
-liveuser:x:1000:liveuser
+adm:x:4:antergos
+wheel:x:10:antergos
+uucp:x:14:antergos
+nopasswdlogin:x:966:antergos
+rfkill:x:983:antergos
+sys:x:3:bin,antergos
+antergos:x:1000:antergos