The linked item selection model is a non-UI component.

So, put it into the right place for that (it's used in common/ rather than
ui/ anyway).
Split out model handling from the property widget.

This still needs to be completed with everything else that is independent
of the UI and needs to run inside the probe.
Integration of the property controller.

For the object inspector we now see the property views in the client as
well, and can edit them.
Move some of the signal monitoring code here.
Integration of NetworkObject for performing method calls.
Move invoke/connect action to the controller.

Connect works already, invoke needs some more work to split up UI and the
argument model.
Implement the remaining set[Meta]Object methods.
Remove a bunch of code that has been moved to PropertyController.
Properly set up the connection models.
Make display state handling work in the client as well.
Split the method invocation code into probe and client parts.

We can now call methods from the client, including providing arguments.
Remove all dependencies to to probe code from the property widget.
Move property widget to ui/.
Don't send the activation signal if we are showing a QMetaObject.
Port all property widget instances to use the property controller.