workbook::operator== was comparing the value of the raw pointer held by two std::unique_ptr's. By definition, this is always false in a well behaved program (if it's true, things go bang...). This then led to adding equality operators to nearly every other struct/class in xlnt to support workbook::operator==
workbook::load and the non-default ctors for loading data from a file are tested using the now functional equality operator
NOTE: a large number of copy ctors need updates/fixing. Many should be defaulted
- hyperlinks to cells and ranges are complete
- hyperlink::display is now set as well as the cell value (in excel these can be different)
-- if a cell is empty, display is equal to value text
-- if a cell has a value, display can be just about anything
- This version copies excel in that display is completely ignored once value is set
- All hyperlink tests are now part of the cell test suite (not the worksheet test suite which the majority were previously located)
