Fix some warnings

[krOoze]

• settingsDialog and submitDialog does not use f; should call a super with it?
• parentItem is shadowed -> just enclose sparse props into block
• widget name is twice in qt ui
• reading device layers seems subtly wrong (though would work given they are deprecated)
• maintenance3 props seem to have been queried twice
• preinitialize some members
• deal with "unitialized member" warnings when using agregate initializer.

[SaschaWillems]

This fails CI on Linux:

vulkanDeviceInfo.cpp:91:66: error: no matching function for call to ‘std::vector<VulkanLayerInfo>::push_back()’ this->layers.push_back({layerProps, layerExtensionsProps});

Can you revisit that change?

[krOoze]

@SaschaWillems Builds now.