Add the copyright information in a dedicated file.

Change-Id: I698040ee2a12e4f2a93f0f9d74d8c6ad6599abb8

COPYRIGHT

+ETSI FORGE COPYRIGHT STATEMENT 
+
+Copyright (c) ETSI 2017. 
+
+This software is subject to copyrights owned by ETSI. Non-exclusive permission is hereby granted, 
+free of charge, to copy, reproduce and amend this file under the following conditions: It is 
+provided "as is", without warranty of any kind, expressed or implied. 
+
+ETSI shall never be liable for any claim, damages, or other liability arising from its use or 
+inability of use. This permission does not apply to any documentation associated with this file 
+for which ETSI keeps all rights reserved. The present copyright notice shall be included in all 
+copies of whole or part of this software and shall not imply any sub-license right.