Qualifying relations with dates and/or date spans

[cjerrysimmons]

We had this request from a recent MITRE Corporation trainee during May SNACSchool. The request is to add a function where editors can qualify relationships with a date or date span. For example, when two people are linked as having the option to add a date that further qualifies that spousal relationship ...

Mitchell, Margaret
Upshaw, Red
1922-1924

  <spouseOf> Marsh, John </spouseOf>
  <dates> 1925-1949 </dates>

Also, to describe the time span of a relationship between a person and a corporate body:

Jobs, Steve
Apple Inc.
1976-2011

Apple, Inc.
Jobs, Steve
1976-2011