Add Duplicate Interrupt button to Edit Interrupt window

[Kamayana]

Adds a button to the Edit Interrupt window that duplicates the currently opened interrupt, adds it to the selected caravan, and switches to editing that duplicate. Closes pyanodon/pybugreports#1245, though parameters aren't supported.

• The duplicate will have an * appended to the end.
  • Unless the name text field was being edited, in which case it will have that name instead.
• Any unsaved changes made in the Edit Interrupt window will be applied to the duplicate, leaving the original interrupt unchanged. Think of it like "Save As" vs. "Save".
• I originally wanted to go with the "name copy", "name copy (2)" naming scheme used in windows, but I couldn't figure out how to make localized names work in this case, since here it's being used as both the actual name and the internal lua key, so I kept getting a "Value must be a string in property tree at ROOT.text" crash.
• When Delete Interrupt is clicked, the duplicate button is hidden until the deletion is confirmed or not.