cleanup:

"GroupName" -> "SongGroup" to make room for CourseGroup
replace checks for "cvs" with a call to StripCvs()
m_Rows -> m_pRows
broadcast on preferred group changes

stepmania/src/MessageManager.cpp

@@ -48,6 +48,8 @@ static const CString MessageNames[] = {
 	"PlayersFinalized",
 	"AssistTickChanged",
 	"AutosyncChanged",
+	"PreferredSongGroupChanged",
+	"PreferredCourseGroupChanged",
 };
 XToString( Message, NUM_MESSAGES );