Merge remote-tracking branch 'origin/translation' into staging

Conflicts:
	Documentation/notation/percussion.itely

diff --cc Documentation/es/extending/programming-interface.itely
Simple merge

diff --cc Documentation/es/notation/simultaneous.itely
Simple merge

diff --cc Documentation/fr/notation/percussion.itely
Simple merge

diff --cc Documentation/fr/notation/simultaneous.itely
Simple merge

diff --cc Documentation/fr/notation/vocal.itely
Simple merge