Add project-wide license file
Add project-wide license file

Change-Id: I8689bf401c16b4b06b02ce08c27953f9befeadde
Signed-off-by: Robert Varga <b8bd3df785fdc0ff42dd1710c5d91998513c57ef@cisco.com>

opendaylight/yangtools,NovusTheory/yangtools,opendaylight/yangtools,522986491/yangtools