re-run unchanged but for date

To allow me to use Git as a Diff to see what changes.
First try at no more than one <birth>

At present I just take the first source which has <birth> information in
the column order (in Authors, first GEDSH, then Barsoum, then VIAF) and
ignore all the rest.
made template date-attributes not recursive

I simplified the template date-attributes to make it not recursive.
multiple sources for birth, death, floruit

Now the birth, death, and floruit elements cite all relevant sources for
these events, regardless of whether there is conflicting assertions.