Doc split: "program usage"

[Graham Percival]

I'd like to have a new manual "book": Program usage.  This book would 
include the INSTALL docs, and chapters 13-15 (running lilypond, 
lilypond-book, and converting) from the existing manual.  Basically, the 
"user manual" deals with the .ly file format, and the "program usage" 
does everything else.  I've never been happy with the final chapters of 
the current user manual; I think this is the right solution.

Unfortunately, this requires some playing with low-level texinfo and the 
makefiles; I'm not comfortable with either of them.

John, I think you're quite familiar with our build system and whatnot 
from all the translation stuff -- could you create the basic framework 
for this?  Once it's there, I'll rewrite the INSTALL, potentially add 
chapters, potentially rework the current chapters 13-15 (in the new 
document), etc; I'm just not certain how to get our build system to 
compile docs from:

lilypond.tely
program.tely

in the same directory.  (assuming that it's ok to have this in 
Documentation/user/   ... I suppose that another option is to create 
Documentation/program/ )

Cheers,
- Graham