The kit drop down on the Examples screen should default to the SDK kit

For example, when installing the Qt SDK, it would be nice if the kit drop down on the Examples screen defaulted to the auto-detected kit from the SDK the first time it is opened (I see that the selected item is remembered between sessions, so we shouldn't override it every time Creator launches). This may only be an issue for users who want to play with a new Qt version, but have existing kits sitting around.