DOC: add description of -dinclude-settings (issue4169053)

[ColinPKCampbell]

Reviewers: ,

Message:
Revises and replaces Reinhold's patch in issue 4129053

Description:
DOC: add description of -dinclude-settings

Adds menu reverences and a description of using -dinclude-settings
on the comand line, to change among various global parameters
such as paper or font size.

Please review this at http://codereview.appspot.com/4169053/

Affected files:
  M Documentation/notation/input.itely


Index: Documentation/notation/input.itely
diff --git a/Documentation/notation/input.itely  
b/Documentation/notation/input.itely
index  
1ef43544237ac75af708688016130c7cd0949494..122654c9f11144219f41d04508ee4994f30d3f11  
100644
--- a/Documentation/notation/input.itely
+++ b/Documentation/notation/input.itely
@@ -1113,6 +1113,7 @@ structure while leaving the notation untouched.
 @menu
 * Using variables::
 * Using tags::
+* Using global settings::
 @end menu

 @node Using variables
@@ -1331,6 +1332,33 @@ than one tagged section at the same place.

 @end ignore

address@hidden Using global settings
address@hidden Using global settings
+
address@hidden include-settings
+
+Global settings can be kept in separate files, which are selected
+on the command line:
+
address@hidden
+lilypond -dinclude-settings=MY_SETTINGS.ly MY_SCORE.ly
address@hidden example
+
+Groups of settings such as page size, font or type face can be stored
+in separate files. This allows different editions from the same score
+as well as standard settings to be applied to many scores, simply by
+specifying the proper settings file.
+
+This technique also works well with the use of style sheets.
+See @rlearning{Style sheets}
+
address@hidden
+Learning Manual:
address@hidden pieces with variables}.
+
+Notation Reference:
address@hidden LilyPond files}.
+
 @node Text encoding
 @subsection Text encoding