Updated license headers to use new GPL-EXCEPT header instead of LGPL3 one
(in those files which will be under GPL 3 with exceptions)

Change-Id: I0a5ed401e2060999694063aeecbdb598246629d7
Reviewed-by: Sergey Belyashov <Sergey.Belyashov@gmail.com>
Reviewed-by: Jani Heikkinen <jani.heikkinen@theqtcompany.com>