sync capture type with preferences

Assets/Util/Preferences.cs

@@ -19,6 +19,11 @@ public class Preferences : MonoBehaviour {
         data.Save();
     }
 
+    public void SetUseLoopback(bool v) {
+        data.useLoopback = v;
+        data.Save();
+    }
+
     public Gradient Theme() {
         return themeSelector.CurrentTheme();
     }