Update incipit snippets

This is in response to Issue 3981, which identified multiple methods of creating incipits in the LSR and docs.  I have deleted 2 of the LSR snippets in the LSR and updated the 3rd to match the syntax introduced in 2.19.16.  I have imported the LSR and edited the templates to use the newly named snippet.  Finally nuked build and rebuilt docs with success.

Since this is almost all LSR work, we wouldn't normally actually review it, but I'd like a patchy sanity check and ditto from contributors.

[PhilEHolmes, 2015-05-06 09:34:38]

Please review

[Trevor Daniels, 2015-05-06 11:40:57]

I haven't checked incipit.ly, but otherwise it looks fine apart from what
appears to be an inadvertent change which needs investigating.

https://codereview.appspot.com/235980043/diff/1/Documentation/snippets/conduc...
File Documentation/snippets/conducting-signs,-measure-grouping-signs.ly (right):

https://codereview.appspot.com/235980043/diff/1/Documentation/snippets/conduc...
Documentation/snippets/conducting-signs,-measure-grouping-signs.ly:31: setting
in @@file@{scm/time-signature-settings.scm@}:
Is this change intentional?  The original looks right.  Looks like someone
edited this snippet in Documentation/snippets without adding the change to
snippets/new.

[email_philholmes.net, 2015-05-06 15:38:24]

----- Original Message ----- 
From: <tdanielsmusic@googlemail.com>
To: <PhilEHolmes@googlemail.com>
Cc: <lilypond-devel@gnu.org>; <reply@codereview-hr.appspotmail.com>
Sent: Wednesday, May 06, 2015 12:40 PM
Subject: Re: Update incipit snippets (issue 235980043 by 
PhilEHolmes@googlemail.com)


>I haven't checked incipit.ly, but otherwise it looks fine apart from
> what appears to be an inadvertent change which needs investigating.
>
>
>
https://codereview.appspot.com/235980043/diff/1/Documentation/snippets/conduc...
> File Documentation/snippets/conducting-signs,-measure-grouping-signs.ly
> (right):
>
>
https://codereview.appspot.com/235980043/diff/1/Documentation/snippets/conduc...
> Documentation/snippets/conducting-signs,-measure-grouping-signs.ly:31:
> setting in @@file@{scm/time-signature-settings.scm@}:
> Is this change intentional?  The original looks right.  Looks like
> someone edited this snippet in Documentation/snippets without adding the
> change to snippets/new.
>
> https://codereview.appspot.com/235980043/

Looks like it's a change been made in the LSR, to try to use the file format 
of TeX, but which gets escaped when it's exported.

I guess the simplest fix is not to bother with @file in the snippet, but 
just use <code></code>

I'll do this soon, but not necessarily as a part of this specific patch, if 
that's OK.

--
Phil Holmes