core: Add BSD 2-Clause license to configuration format header

core: Add BSD 2-Clause license to configuration format header

This avoids having to distribute configuration files for target systems
under GPL terms. It also allows to process those files with differently
licensed management tools.

Contributions came from Valentine, Henning and me. I'm signing off for
Henning as well in the name of Siemens.

CC: Valentine Sinitsyn <valentine.sinitsyn@gmail.com>
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Valentine Sinitsyn <valentine.sinitsyn@gmail.com>