Suggested improvement to validation for marriage submissions

If a marriage entry has the "present" flag set (ie marriage continues until the present day) and the entry is then modified to add an end date (eg when the person or their spouse has just died), the "present" flag overrides the fact that an explicit date is supplied. and the explicit date is ignored.

I suggest that the form validation is modified to check for the presence of both "present" and an explicit end-date and to generate a warning, and maybe by default turn off the "present" flag in this situation.

It would save mistakes like 140118-100838-563000 where I supplied an end-date because Roger Lloyd-Pack has just died but didn't notice that there was already a "present" flag that I should have unticked.