[PATCH 07/73] Add the list of contributors agreeing to LGPL licensing

[PATCH 07/73] Add the list of contributors agreeing to LGPL licensing

* List of contributors, with short explanation
* added LGPLv3 license text as COPYING-LGPL
* moved GPLv3 license text to COPYING-GPL
* COPYING still contains the GPLv3, but with an explanation that new
  code is LGPL
* updated the contribution guide
* Removed the GPL license header from Readme, added explanation.

Signed-off-by: Marcus Müller <marcus@hostalia.de>
Gbp-Pq: Name 0007-Add-the-list-of-contributors-agreeing-to-LGPL-licens.patch