[MlMt] Smart mailbox for "today", etc.

[John D. Muccigrosso]

I like to have “date is today” instead of “within last day”. 
Ditto for “yesterday”. It’s nice to have last week or month too, 
but I can live with the slight variation in the window on those when the 
window doesn’t quite start at midnight. For “today” though, I 
really want “today” and not the last 24 hours.

I see there are several old requests on the mailing list for this (2013 
and 2014), but I wanted to put in another request for it.

John