Some fixes in the add prop. to sdf wizard

This pull request fixers the following things:
* Make the listeners for the comboboxes to check if they are the source (i.e. fixes bug 3504)
* Make the SDFPropertiesImportWizard import properties when adding a own name as well  (i.e. fixes bug 3505)
* Updates the navigator, when the new sdf-file has been created by the SDFPropertiesImportWizard. So the new file becomes visibly in the navigator without the user have to make a refresh
* Makes the open-file-dialog to start in the selected workspace root. So now it will be easier to find the wanted file.
* Removes a NPE that came if pressing cancel in the open-file-dialog when
adding a properties file. I notised this when fixing the path thing in the point above.