Fix dimensions for several output variables
* Dimensions for the following output variables are now
interpreted correctly since they have been added to the
dimension-variables variable (heeding the warning at the
top of ly/paper-defaults.ly):
after-title-space
before-title-space
between-title-space
bottom-margin
foot-separation
head-separation
top-margin
* page-turn-page-breaking-badturns.ly: slightly adjusted
* NR 4.6: general rewrite, with updated information
Signed-off-by: Patrick McCarty <pnorcks@gmail.com>