Mesh Tools: Fix the license of "Edge Floor Plan" file

The add-on file had the license as GPL2, but for it to be compatible
with Blender it has to be GPL or later.

mesh_tools/mesh_edges_floor_plan.py

@@ -2,8 +2,8 @@
 #
 #  This program is free software; you can redistribute it and/or
 #  modify it under the terms of the GNU General Public License
-#  as published by the Free Software Foundation; version 2
-#  of the License.
+#  as published by the Free Software Foundation; either version 2
+#  of the License, or (at your option) any later version.
 #
 #  This program is distributed in the hope that it will be useful,
 #  but WITHOUT ANY WARRANTY; without even the implied warranty of