* lily/parser.yy (relative_music): start at middle C without pitch

* lily/parser.yy (relative_music): start at middle C without pitch
argument.

* Documentation/user/changing-defaults.itely (Page layout): new node.
(Paper size): rename node
(Page breaking): new node.
(Titling): move from invoking.
(File structure): new node.

* lily/parser.yy (score_body): allow \header and music anywhere in
\score body.