Allow 0/1 for boolean cell values

[twsouthwick]

Fixes #887

[twsouthwick]

@tomjebo Can you verify that a 0 or 1 are valid boolean values for cells?

[tomjebo]

From MS-OI29500 2.1.659: ...If the cell contains a Boolean, the value shall be 1 to specify true and 0 to specify false.

[twsouthwick]

So can it be true or false as well, or only 1/0?

[tomjebo]

Yes, but they MUST be lower case. Excel reads this as lower case "true" or "false" but will only write as "0" or "1". Excel will throw a message dialog and ask to "correct" the underlying XML if the type is "b" and the value is anything but "0", "1", "true", or "false".

[twsouthwick]

Thanks @mkorsukov for the comments!

[twsouthwick]

@tomjebo can you take another look and approve if it looks good? I'd like to get this out as a 2.12.3 release

[igitur]

Yes, but they MUST be lower case. Excel reads this as lower case "true" or "false" but will only write as "0" or "1". Excel will throw a message dialog and ask to "correct" the underlying XML if the type is "b" and the value is anything but "0", "1", "true", or "false".

Thanks, this actually highlighted some issues in ClosedXML. We were writing out Boolean values using propercasing. Nobody every complained, though.