The model is mainly responsible for providing the property handlers. Additionally,
it can provide user interface names and help URLs for property categories.
Note that there are two ways of setting or retrieving the current model: You can either
use ::com::sun::star::frame::XModel::setModel, or, if you do not want
or need to implement the full-blown ::com::sun::star::frame::XModel interface,
you can use this property directly. Both approaches are semantically equivalent.
If a new model is set at the inspector, the complete UI will be rebuilt to reflect
the change, using the new property handlers provided by the new model.