Doc: improve 2.10 World music (issue2732043)

[v . villenave]

Reviewers: ,

Message:
Hi everybody,

here's a patch that will make Trevor happy: no more "musics"! :-)

Please have a look; I am currently building the docs to make sure that
it doesn't break anything, but I'm hopeful.

Cheers.

Description:
Doc: improve 2.10 World music

* Move Turkish note names table in the relevant subsection;
* Add glossary entries (with stubs)
* Add @seealso whereever possible
* Improve wording, consistency.

Please review this at http://codereview.appspot.com/2732043/

Affected files:
  M Documentation/music-glossary.tely
  M Documentation/notation/world.itely