Copyright and License header put in most files

A further check is needed, but now all files have their Copyright + License
header.
Header is compliant with the following template:

/*
 * Copyright (c) dog hunter AG - Zug - CH
 * General Public License version 2 (GPLv2)
 * Author: Name Surname <mailaddress>
 */

Signed-off-by: Aurelio Colosimo <aurelio@aureliocolosimo.it>