Doc: Renamed Qt Quick Code Samples page.

-new name is Qt Quick Examples and Tutorials
-includes tutorials, not just examples or code samples.

Task-number: QTBUG-36838
Change-Id: I660770cac1cdd71cd3b34bad878b0e59a088924b
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@digia.com>