#9 Import entities from an xmpuzzle library

[George Bell]

It would be nice to have the ability to import pieces from another xmpuzzle file. For example, one could keep a large library of polyomino pieces in one file. For a new puzzle, suppose I want to select a subset of these pieces to use. I import from the library, which opens a dialog box of all the pieces in the library. I check those that I want, and they are imported into the new file.