all-caps vs all-lowercase `FALSE` and `TRUE`

[TallTed]

Tracking issue for eventual editorial push.

Originally posted by @TallTed & @afs in #265 (comment)

[@TallTed] I noticed these all-caps FALSE and TRUE not far above in the same paragraph, in marked contrast to the lowercase true/false elsewhere in the documents. I think we should be consistent with these. I am inclined to the all-caps, but open to arguments for the lowercase.

[@afs] This is part of general update of the presentation and there are other cases of this to clear-up. We can agree some display principles and apply them, available resources depending.