showing exceptions during parsing to the user is a table
Minor changes to the layout of the ReviewExtractedItemsPage

- layout: use form attachment so that resizing the dialog will also
  resize the tables
- layout: show only the error message to the user; the class name of the
  exception is too technical and available in the log
- extraction: use a Job instead of container#runWithProgress because
  the latter is synchronous
- context menu: attach context menu to the extracted items list

Issue: #197