Doc:Updated links in the header.
Doc:Updated links in the header.

-'Labs' was removed
-changed links to point to 'qt-project.org' or to Digia sites.

Task-number: QTBUG-27591
Change-Id: I065068666a8b7590d0303f2e9c7346dfba6adf3d
Reviewed-by: Martin Smith <a8cc6484db2755056ccf1c457da8ca771f895dea@digia.com>

kobolabs/qtdoc,kobolabs/qtdoc,kobolabs/qtdoc,kobolabs/qtdoc