update games/default
LuaPerlinNoiseMap: Fix 3d noise safety check
Update german translation
Provide more info if a subgame is not valid/found
Fix misleading error when exiting the client from the main menu
Revert "Update Russian translation"

This reverts commit e4e4324a30d6bcac5cc06c74e955e4941b14bd38.

Conflicts:
	po/minetest.pot
	po/*/minetest.po
Merge remote-tracking branch 'minetest/master' into stable
Merge remote-tracking branch 'origin/stable'