-V (and -X) now respects a report end date set with -e/-p/date: when
choosing the valuation date, similar to hledger 1.14 and Ledger.
This means that -V/-X aren't exactly like either --value=end or
--value=now. The "Effect of --value on reports" doc has been extended
accordingly, and much of it has been reworded and made more accurate.
