Merge pull request #408 from PeterBjuhr/musicxml

MusicXML integration with ly.music wip
fix #409
Export Audio Feature
Merge pull request #412 from ryanmichaelmcclure/master

beginnings of Export Audio Feature
put fr.po back

(dont know how I managed to delete it!)
fr tr
Merge pull request #414 from philmassart/master

fr tr
pitch lang "deutsch": understand "asas" as "ases"

never knew this note existed :-)
Duplicate classes
Using class name KeySignatureMode instead of UserCommand; fix #418