lots of changes

- GUI: ability to load files
- GUI: arrow key navigation
- fix sample volumes

src/engine/engine.h

@@ -90,7 +90,6 @@ class DivEngine {
   void processRow(int i, bool afterDelay);
   void nextOrder();
   void nextRow();
-  void reset();
   // returns true if end of song.
   bool nextTick();
   bool perSystemEffect(int ch, unsigned char effect, unsigned char effectVal);
@@ -113,6 +112,9 @@ class DivEngine {
     // stop
     void stop();
 
+    // reset playback state
+    void reset();
+
     // get sys channel count
     int getChannelCount(DivSystem sys);