Document merge changes

[tim-pearce]

Apologies for doing this way. Don't have time to do a full pull and merge request.

This is my version of the class:- call_document_merge.class.txt

It should work as before except for the bit with the comment // NB below we use keys from $headerrow, such as "suburb" // AND raw keys such as "address_suburb", to support both new and legacy formats.

I use familyid in my spreadsheet to detect change of family when they have the same name. (I would attach the file but github [being Microsoft owned now] won't allow upload of .ods files).

Also added _cr fields. Where there are line breaks this will insert "&CHAR(10)&" in the output, thus replicating the line break in a spreadsheet.

There's also a $extra array in GetMergeData and, to tell the truth, I don't remember what it does!

Tim