Initialize the server and register models a lot earlier.

This is needed since the tools are going to rely on this during non-UI
initialization, which happens right after we returned from the Probe ctor.
Don't exclude the object inspector from initialization.
Add a second version of the StandardToolFactory for core/ui splitting.

It's only a migration aid, eventually we need entirely separated factories
for probe and ui parts.
Split the object inspector into probe and UI parts.

This also initializes the probe part outside of the UI code path, which
means we now also have the object inspector available if the server is
not showing the UI, ie. in Q[Core|Gui]Applications.
Properly integrate the object inspector into the client.