By default, when an Xlsx spreadsheet is read, its calculation engine is set to `RETURN_ARRAY_AS_VALUE` for array formulas. The user does have the option to change this. However, the presence of certain metadata in the file indicates that it was saved as if `RETURN_ARRAY_AS_ARRAY` was in use. This PR tests for the metadata, and, if present, sets `...ARRAY` rather than `...VALUE`. This eliminates the need for any extra action on the user's part.
oleibman