export: fixed many export formats including still image and image sequence export

Still incomplete, but does a lot towards #1345

app/codec/exportcodec.h

@@ -33,6 +33,7 @@ class ExportCodec : public QObject
   Q_OBJECT
 public:
   enum Codec {
+    // Video codecs
     kCodecDNxHD,
     kCodecH264,
     kCodecH265,
@@ -40,11 +41,16 @@ public:
     kCodecPNG,
     kCodecProRes,
     kCodecTIFF,
+    kCodecVP9,
 
+    // Audio codecs
     kCodecMP2,
     kCodecMP3,
     kCodecAAC,
     kCodecPCM,
+    kCodecOpus,
+    kCodecVorbis,
+    kCodecFLAC,
 
     kCodecCount
   };
@@ -53,8 +59,6 @@ public:
 
   static bool IsCodecAStillImage(Codec c);
 
-  static QStringList GetPixelFormatsForCodec(Codec c);
-
 };
 
 }