Add model registration to ProbeInterface.

More convenient for internal tools, and makes remote models for plugins
possible without having access to all the internals.
Use new registerModel() method instead of duplicating this code everywhere.
Move the ObjectBroker into a shared library.

Otherwise we create several instances if we link it into plugins, which
of course is a problem for a singleton.
Load the plugin also when we only ask for the widget.

This happens when being used in the client.
Load plugins inside the client as well.
Core/UI split for the timer profiler plugin.

The periodic view update still needs to be moved to the model, wont work
remotely due to model data being cached.
Core/UI split of the mimetype browser.

Makes it work remotely, even with a Qt4 client.
Core/UI split for the locale inspector, making it work remotely.
Properly work with lazy-loaded models.