Use baptism date for children autosort where birth date is not available

[burtek]

v3.8.0 introduced additional dates being displayed on a chart:

Added option in tree diagrams - use additional dates (baptism, burial) if the main ones (births, deaths) are missing

This is very good as in many cases the church books only included baptism date rather than birth date. This should however (IMO) extend to autosorting children as well. Autosort works well on children with birth dates defined, but it doesn't work at all when baptism dates are used instead (and makes things even worse if only some of the children have birth date, while others baptism date due to how the church books style changed). Right now there is no way (that I know of) to sort the children manually in such case.