Doc: Update the list of highlighted examples

Remove highlighting for a number of older and less relevant examples.
Add examples from new modules, and examples that have been visually
polished.

Task-number: QTBUG-37203
Change-Id: I4e9be9a54f1ecea3bb407c049c1d44a7c00333a6
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@theqtcompany.com>
Reviewed-by: Topi Reiniö <topi.reinio@digia.com>