Add copyright to all files; modify textures a bit

Make them indexed and improve the "on" look.

LICENSE.md

@@ -1,7 +1,7 @@
-Digiplay - Copyright © Pedro Gimeno Fortea.
+Digiplay - Copyright © 2017 Pedro Gimeno Fortea.
 
-This file is part of the package Digiplay. Both copying and distribution 
-of this package are permitted, with or without modification, under the 
-sole condition that the copyright notice or notices and this notice are 
-preserved. This package is offered as-is, without any warranty express 
+This file is part of the package Digiplay. Both copying and distribution
+of this package are permitted, with or without modification, under the
+sole condition that the copyright notice or notices and this notice are
+preserved. This package is offered as-is, without any warranty express
 or implied.

init.lua

@@ -1,4 +1,18 @@
--- Copyright © 2017 Pedro Gimeno Fortea.
+--[===============================================================[--
+
+Digiplay - Copyright © 2017 Pedro Gimeno Fortea.
+
+This file is part of the package Digiplay. Both copying and distribution
+of this package are permitted, with or without modification, under the
+sole condition that any copyright notices and this notice are preserved.
+This package is offered as-is, without any warranty express or implied.
+
+--]===============================================================]--
+
+-- Informative note: The textures included in the package are under the same
+-- license; the files include a valid tEXt chunk with the copyright and
+-- license notice.
+
 
 local function multicolour_light_on_punch(pos, node, puncher, pointed_thing)
   local channel = minetest.get_meta(pos):get_string("digich")