Update license headers and add new licenses

- Renamed LICENSE.LGPL to LICENSE.LGPLv21
- Added LICENSE.LGPLv3 & LICENSE.GPLv2
- Removed LICENSE.GPL

Change-Id: I173cdbf20a35132737586a9cdbfc2a6f209f6d6a
Reviewed-by: Jani Heikkinen <jani.heikkinen@digia.com>