make NetworkInterface compile on WEC2013 again
LICENSE: add info about SPDX-License-Identifier usage and use it

fix: remove executable flag and change back to 100644 (was 100755)

Signed-off-by: Roger Meier <r.meier@siemens.com>
Merge pull request #444 from bufferoverflow/spdx3

LICENSE: add info about SPDX-License-Identifier usage and use it
Merge remote-tracking branch 'upstream/develop' into develop