Add very crude integration of the object tree.

This is full of hacks, but it shows a path forward.
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.
Crude integration of the property controller.

For the object inspector we now see the property views in the client as
well, and can edit them.
QSFPM triggers this assert by calling index() during begin/endInsertRows.

Still needs to be investigated.
Move some of the signal monitoring code here.
Test 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.
Crude integration of the widget inspector.
Split the method invocation code into probe and client parts.

We can now call methods from the client, including providing arguments.