Update license headers and add new licenses

- Added LICENSE.LGPLv21, LICENSE.LGPLv3 & LICENSE.GPLv2

Change-Id: If5b04ddf25095ae1eb59e25361c88e570bb2b4df
Reviewed-by: Antti Kokko <antti.kokko@digia.com>
Reviewed-by: Tony Sarajärvi <tony.sarajarvi@digia.com>