Using markup-like functions outside of markup (layout/props)

[Kyle Baldwin]

Hello - 

I'm trying to use the `book-first-page` scheme function to write the first page 
to a file in order to do some automated score processing. `book-first-page` 
takes the layout and props arguments, however, I'm having a hard time wrapping 
my head around accessing the layout and props properties without using a 
\markup command. 

Does anyone have any guidance on this and/or a better way to get the first page 
programmatically. Thank you! 

-Kyle