Handling of AFT and BEF in 7.1

[dthaler]

Discussed in steering committee

• The first version is shorter and probably better than the second version
• Copying exclusive entry to exclusive meaning loses precision, but does not assert a falsehood
• The ambiguity is less extreme with more precise dates (AFT 1 JUN 1850 has only 24 hours of ambiguity, while AFT 1850 has 365 days of ambiguity)
• There may be some language difference, where English and German (two languages spoken by steering committee members) having different likelihoods of accepting the inclusive definition.
• We could deprecate using AFT/BEF with imprecise dates -- this could help rectify some of the ambiguity. An automated tool could turn all AFT 1850 to either AFT 31 DEC 1850 or AFT 1 JAN 1850 depending on the culture/interpretation selected by the user.

Originally posted by @tychonievich in #775 (comment)

This issue tracks what the replacement is in 7.1, continuing discussion on the last bullet point above.