Doc: Edited list of UI topics in the User Interface page.

-list should be the same as the one from the QML Application Developer
Resources page.
-the use case pages are a better fit than the concept pages because
they cover more than just Qt Quick.

Change-Id: Icb09349cc1490fa0b5157c9983d09baae55d9a68
Reviewed-by: Martin Smith <martin.smith@digia.com>