Refreshes the contents of the TJamShellControl base class.
Use the FullRefresh() method if you want to refresh the contents of a TJamShellControl. Usually you don't have to call FullRefresh() manually. It will be called automatically, when e.g. the Path property changes, or the connected ShellLink reports a change. Derived classes have to implement the IJamShellControl.Refresh() method and decide which visual elements have to be refreshed.