Removed some unused icons

SoniControl/app/src/main/res/drawable/button_stop.xml

-<?xml version="1.0" encoding="utf-8"?>
-<selector xmlns:android="http://schemas.android.com/apk/res/android">
-    <item android:drawable="@drawable/ic_pause_white_48dp" /> <!-- default -->
-</selector>
\ No newline at end of file

SoniControl/app/src/main/res/layout/activity_main.xml

@@ -54,7 +54,7 @@
         android:layout_alignStart="@+id/btnPlay"
         android:layout_alignTop="@+id/btnSettings"
         android:background="@android:color/darker_gray"
-        android:src="@drawable/button_stop" />
+        android:src="@drawable/ic_pause_white_48dp" />
 
     <ImageButton
         android:id="@+id/btnExit"