-Added new intents to append streams to current player.

-Added long clicks for popup and background player buttons on details fragment for append intents.
-Removed restrictions for preventing UI to show up when player is buffering.
-Fixed icons for all repeat modes.
-Added Progress bar to background activity when player is in not ready state.
-Fixed Track Selection when switching between video and audio only on video players.
-Fixed video player to enable tunnelling only after sdk > 21.
-Fixed activity exception from restarting after service is shutdown on earlier sdk versions.

app/src/main/res/layout/activity_background_player.xml

@@ -183,6 +183,23 @@
             android:src="@drawable/ic_pause_white"
             tools:ignore="ContentDescription"/>
 
+        <ProgressBar
+            android:id="@+id/control_progress_bar"
+            style="?android:attr/progressBarStyleLargeInverse"
+            android:layout_width="50dp"
+            android:layout_height="match_parent"
+            android:layout_centerVertical="true"
+            android:layout_centerHorizontal="true"
+            android:layout_centerInParent="true"
+            android:layout_marginLeft="5dp"
+            android:layout_marginRight="5dp"
+            android:background="#00000000"
+            android:padding="2dp"
+            android:clickable="false"
+            android:scaleType="fitCenter"
+            android:indeterminate="true"
+            android:visibility="invisible"/>
+
         <ImageButton
             android:id="@+id/control_forward"
             android:layout_width="40dp"

app/src/main/res/layout/activity_main_player.xml

@@ -155,7 +155,7 @@
                     android:clickable="true"
                     android:padding="5dp"
                     android:scaleType="fitXY"
-                    android:src="@drawable/ic_repeat_white"
+                    android:src="@drawable/exo_controls_repeat_off"
                     tools:ignore="ContentDescription,RtlHardcoded"/>
 
                 <ImageButton