Documentation for cross staff stems

Updated the documentation to take account of the new cross staff stem feature.

[PhilEHolmes, 2012-07-23 16:01:10]

Please review my attempt at some documentation.

[Jean-Charles, 2012-07-23 18:36:00]

Just to be sure I understand correctly!

http://codereview.appspot.com/6432063/diff/1/Documentation/notation/keyboards...
File Documentation/notation/keyboards.itely (right):

http://codereview.appspot.com/6432063/diff/1/Documentation/notation/keyboards...
Documentation/notation/keyboards.itely:426: automatic beams do not beam the
notes on one staff when it’s not
Once I've seen the snippet's code, I understand what you mean: "beware: autobeam
should be switched off somewhere!"

[Keith, 2012-07-23 18:58:02]

http://codereview.appspot.com/6432063/diff/1/Documentation/notation/keyboards...
File Documentation/notation/keyboards.itely (left):

http://codereview.appspot.com/6432063/diff/1/Documentation/notation/keyboards...
Documentation/notation/keyboards.itely:457:
{indicating-cross-staff-chords-with-arpeggio-bracket.ly}
I suggest keeping this in the documentation. It is for situations where you
can't simply join the chord with a stem.

http://codereview.appspot.com/6432063/diff/1/Documentation/notation/keyboards...
File Documentation/notation/keyboards.itely (right):

http://codereview.appspot.com/6432063/diff/1/Documentation/notation/keyboards...
Documentation/notation/keyboards.itely:429: @snippets
The introductory text is on the opposite side of the "Selected Snippets" divider
from the example it introduces.

[PhilEHolmes, 2012-07-25 09:34:58]

Updates from comments.

http://codereview.appspot.com/6432063/diff/1/Documentation/notation/keyboards...
File Documentation/notation/keyboards.itely (left):

http://codereview.appspot.com/6432063/diff/1/Documentation/notation/keyboards...
Documentation/notation/keyboards.itely:457:
{indicating-cross-staff-chords-with-arpeggio-bracket.ly}
Willdo.

http://codereview.appspot.com/6432063/diff/1/Documentation/notation/keyboards...
File Documentation/notation/keyboards.itely (right):

http://codereview.appspot.com/6432063/diff/1/Documentation/notation/keyboards...
Documentation/notation/keyboards.itely:426: automatic beams do not beam the
notes on one staff when it’s not
The code will automatically appear in the documentation, because of the
[verbatim] so this should make it clear.

http://codereview.appspot.com/6432063/diff/1/Documentation/notation/keyboards...
Documentation/notation/keyboards.itely:429: @snippets
Don't think I understand 'opposite side'.