Invalidation means that any user interface representation (such as toolbox buttons), or
any dispatches associated with the features in question are potentially out-of-date, and
need to be updated.
Parameter Features
The set of features whose state might have changed.
This method is used of it cannot be exactly and reliably determined
which features might actually have changed their state. In this case, the callee
should assume all features it is interested in must be requeried.
