Add license header to RST files

Add license header to RST files

Add the required license header to all .rst files under the docs folder
in the repository and a LICENSE file to the image folders.

The patch also extends the list of authors in the index.rst file of the
requirements document.

Change-Id: Icf8b2c36425769512f0ba9072766ac9bc22c0955
Signed-off-by: Ildiko Vancsa <ildiko.vancsa@ericsson.com>