Update documentation for MIDI articulations. (issue 38420044)

[tdanielsmusic]

LGTM, apart from a slight rewording.


https://codereview.appspot.com/38420044/diff/1/Documentation/notation/input.itely
File Documentation/notation/input.itely (right):

https://codereview.appspot.com/38420044/diff/1/Documentation/notation/input.itely#newcode2891
Documentation/notation/input.itely:2891: @ref{The Articulate script}
adds the following items to the above list:
While you're changing this sentence, could it be
reworded to put the @ref at the end?  It looks
better that way in the pdf.
Like this:
"A script is available which adds the following items
to this list, see @ref{The Articulate Script}:"

Trevor

https://codereview.appspot.com/38420044/