Update incipit snippets (issue 235980043 by address@hidden)

[PhilEHolmes]

Reviewers: ,

Message:
Please review

Description:
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.

Please review this at https://codereview.appspot.com/235980043/

Affected files (+298, -701 lines):
  M Documentation/ca/learning/templates.itely
  M Documentation/cs/learning/templates.itely
  M Documentation/de/learning/templates.itely
  M Documentation/es/learning/templates.itely
  M Documentation/fr/learning/templates.itely
  M Documentation/it/learning/templates.itely
  M Documentation/ja/learning/templates.itely
  M Documentation/learning/templates.itely
  M Documentation/nl/learning/templates.itely
  M Documentation/snippets/ancient-notation.snippet-list
  D  
Documentation/snippets/ancient-notation-template----modern-transcription-of-mensural-music.ly
  M Documentation/snippets/conducting-signs,-measure-grouping-signs.ly
  M Documentation/snippets/incipit.ly
  A Documentation/snippets/new/incipit.ly
  M Documentation/snippets/real-music.snippet-list
  M Documentation/snippets/really-cool.snippet-list
  M Documentation/snippets/specific-notation.snippet-list
  M Documentation/snippets/template.snippet-list
  D Documentation/snippets/transcription-of-ancient-music-with-incipit.ly
  M Documentation/snippets/tweaks-and-overrides.snippet-list
  M Documentation/snippets/workaround.snippet-list