UIA files should be loaded and handled by Qt 3D Studio

UIA files can't be opened or edited by Qt 3D Studio. This is odd as UIA is the "project" file collecting multiple presentations together. UIA files are a bit outside of the tooling scope now that Architect has been removed.

This must be fixed and required things that we must edit must be covered by the UI tool.

One idea would be to load UIA file in to a "container shell" window that then hosts the actual current Qt 3D Studio editor. User could see presentations in the UIA and switch between those and edit other values in more meaningful way than currently.