QtIFW

Update docs. (Qt4, Qt5 support and digia naming).

Change-Id: I08ab41846b7c954ee9ef1ae5c907a35864165e18
Reviewed-by: Kai Koehne <kai.koehne@digia.com>
Reviewed-by: Niels Weber <niels.weber@digia.com>
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@digia.com>