sequence: made divider a sequence parameter rather than a viewer parameter

Doing this makes the preview resolution an explicit project setting rather
than a temporary UI setting. This will allow more consistency when caching.

app/codec/waveinput.h

@@ -48,7 +48,7 @@ public:
 
   bool at_end() const;
 
-  const AudioRenderingParams& params() const;
+  const AudioParams& params() const;
 
   void close();
 
@@ -61,7 +61,7 @@ private:
 
   qint64 calculate_max_read() const;
 
-  AudioRenderingParams params_;
+  AudioParams params_;
 
   QFile file_;