Add LICENSE file

LICENSE file for all repos which contain SW licensed under the GPL as well as SW licensed under the LGPL. This LICENSE file shall be copied to all repos with GPL+LGPL SW, but not for repos that contain SW licensed under the GPL or LGPL only. Details are explained in the upcoming 13MD05-90_SwArchSpec document.

Comment: GitHub displays automatically for each repo the used license type when the license text could be recognized within the LICENSE file. The first listed license text in LICENSE will be recognized as type. Therefore, we list GPL before LGPL license text to get GPL as displayed license type for a mixed license repo.