Documenting the page breaker variables

[Patrick McCarty]

Hello,

The blank-page-force and blank-last-page-force are already documented,
but I noticed blank-after-score-page-force was added last November by
Joe.

I want to include a description of this variable in NR 4.1.2, where
the others are documented.

Could someone enlighten me on the purpose of
blank-after-score-page-force?  I don't understand the relevant C++
code.  Are the descriptions of the already-documented page
breaker variables accurate?

Also, would it be worth adding three regtests to demonstrate how these
variables work if they are modified?

Thanks,
Patrick