LICENSE: Add GPLv3+

Now all source files should follow GPLv3 source licensing.

See GitHub Issue #65.

Signed-off-by: Erik Bernoth <erik.bernoth@gmail.com>
Acked-by: Eik Binschek <binschek@dresearch-fe.de>
LICENSE: Add CC-BY-SA 3.0 to docs

The docs are no source code, so they are shared under CC-BY-SA 3.0.

See GitHub Issue #65.

Signed-off-by: Erik Bernoth <erik.bernoth@gmail.com>
Acked-by: Eik Binschek <binschek@dresearch-fe.de>