TrackRequest: add "keep" flag to change download location.

src/main/java/moe/nekojimi/chords/TrackRequest.java

@@ -43,6 +43,7 @@ public class TrackRequest implements Comparable<TrackRequest>
     private String requestedIn;
 
     private double priority = 1.0;
+    private boolean keepTracks = false;
 
     public YamlMapping toYAML()
     {
@@ -78,6 +79,16 @@ public class TrackRequest implements Comparable<TrackRequest>
         requestedIn = invocation.getRequestMessage().getChannel().getId();
     }
 
+    public boolean isKeepTracks()
+    {
+        return keepTracks;
+    }
+
+    public void setKeepTracks(boolean keepTracks)
+    {
+        this.keepTracks = keepTracks;
+    }
+
 //    public Message getRequestMessage()
 //    {
 //        return requestMessage;