Introducing the new layout for NR 2.1 Vocal music

Introducing the new layout for NR 2.1 Vocal music

"Entering lyrics" has been renamed into
  "Lyrics explained"
"Common notation for vocals" has been renamed into
  "Entering lyrics" (better consistency with NR 1.x.y titles)
"Placement of lyrics" has been renamed into
  "Specific uses of lyrics"

The first section (now called "Entering lyrics") has also been
reorganized.

The German, Spanish and French vocal.itely files have been updated,
but not the po files.