TODO for InfoViewer
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* Allow multiple instances of InfoViewer windows:
  - menu "File": New window, Clone window
  - right-click popup: Open link in a new window
  - new "Windows" menu: quick jump to other InfoViewer windows
* stop button
* progress bar (use EditorPane.getStream())
* Option "InternalBrowser/Appeareance/Join Tool and Addressbar" ?
