applets/clipboard: add test for history records

Test the clipboard widget can save the current clipboard text

• clipboard
  • Copy
    • Copy text (!2509 (merged))
      • Long text is truncated in ListView
      • Text with space/tab/newline is sanitized in ListView
    • Copy image
    • Copy file
  • Edit text
    • Save
    • Cancel
  • Generate barcode
  • History
    • Maximum number of records
    • Delete record
    • Click record
    • Search in history
    • Save history
    • Clear history (Can't test since there is a prompt dialog)
  • Keyboard navigation (TODO use at-spi webdriver)
  • Empty hint