Added ability to scan library in SettingsFragment

app/src/main/java/com/cappielloantonio/play/interfaces/ScanCallback.java

@@ -0,0 +1,8 @@
+package com.cappielloantonio.play.interfaces;
+
+public interface ScanCallback {
+
+    void onError(Exception exception);
+
+    void onSuccess(boolean isScanning, long count);
+}