Duplicate in the libraries browser does not honor one-file setting.

[Christoph <buchner@…>]

In the OMEdit libraries browser, create a package with "Save contents in one file" checked off, and save. Use right-click "New Modelica class" to create a model, and save. It gets created, correctly, as a separate .mo file.

Now, use right-click "Duplicate" to duplicate the new model in the same package, and save.
Expected behaviour: It should also be created as a separate file.
Observed behaviour: Contrary to the specified setting, it does not get created as a separate file, but instead in the package.mo file of the package.

[Francesco Casella]

See #4594, with examples and discussion