Textures: New textures for silver sandstone nodes

mods/default/README.txt

@@ -118,6 +118,9 @@ paramat (CC BY-SA 3.0):
   default_mese_post_light_side.png
   default_mese_post_light_side_dark.png
   default_mese_post_light_top.png
+  default_silver_sandstone.png -- Derived from a texture by GreenXenith (CC-BY-SA 3.0)
+  default_silver_sandstone_brick.png -- Derived from a texture by GreenXenith (CC-BY-SA 3.0)
+  default_silver_sandstone_block.png -- Derived from a texture by GreenXenith (CC-BY-SA 3.0)
 
 brunob.santos (CC BY-SA 4.0):
   default_desert_cobble.png
@@ -202,11 +205,6 @@ npx (CC BY-SA 3.0)
   default_rainforest_litter.png
   default_rainforest_litter_side.png
 
-GreenXenith (CC-BY-SA 3.0):
-  default_silver_sandstone.png
-  default_silver_sandstone_brick.png
-  default_silver_sandstone_block.png
-
 kaeza (CC-BY-SA 3.0):
   default_desert_sandstone.png
   default_desert_sandstone_brick.png