Doc-es: update CHANGES, programming-interface, scheme-tutorial, others.

Also included/helpus, common-notation, learning/fundamental, learning/tweaks,
notation/ancient, changing-defaults.
Doc-es: Update some files in Extending, Learning and Notation manuals.
Doc-es: update Tweaks, Changing defaults, Expressive, Fretted.
Doc-es: update Input, Pitches, Repeats, Rhythms, Simultaneous.
Doc-es: update of Spacing, Staff, Text, Vocal, Wind.

  Also fix doc build from a wrong node ref.
Doc-es: update Usage: External, LilyPond-Book, Running, Suggestions, Updating.

This makes a full update of all Spanish manuals, except LSR snippets and web.
Web-es: update Community, Introduction, News, News-Front.

This makes a full update of the Spanish docs, except LSR snippets.
Doc-es: update changed snippets.
Doc-es: put version mark in texidocs.

This completes a full update of Spanish documentation and web.
Doc: update Translations Status.
Release: bump VERSION_DEVEL.
PO: update template.
Release: update news.
Doc-it: add chapter 1.6 of Notation Reference
Doc-fr: updates LM, NR and usage
Retouch translation status for fr and it
Revert "align-interface.cc: Clarify code for empty staves"

This reverts commit 51560f756aa3ab37592c815062e733998accf79c.
Merge remote branch 'origin/master' into release/unstable
PO: update template.
Release: update news.