Add string ensemble score structure

orchestrallily.ily

@@ -106,6 +106,10 @@ conditionalBreak = #(define-music-function (parser location) ()
   ("VocalScore" "SimultaneousMusic" ("Singstimme" "Pfe"))
 ))
 
+#(define oly:StringEnsembleScoreStructure '(
+  ("FullScore" "StaffGroup" ("VI" "VII" "Va" "Vc" "Cb" "VcB"))
+))
+
 #(define oly:fullOrchestraScoreStructure '(
 ; Part-combined staves for full score
   ("Fl" "PartCombinedStaff" ("FlI" "FlII"))