Add KTitleWidget class. This is a widget that can be used for headers (e.g. for a dialog title). It looks like the titles from the current about dialogs and config dialogs. This new class reduces code duplication and keeps the design code in one central place. This way we can easier change its look and keep it consistent.

This change does not break any existing code!

Agreed on kde-core-devel (and #kde4-devel).