Update license headers and add new licenses

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

Change-Id: Iad800f28f4e85e3f00512400ed9c5ed196c5097a
Reviewed-by: Antti Kokko <antti.kokko@digia.com>
Reviewed-by: Tony Sarajärvi <tony.sarajarvi@digia.com>