Black theme update (#673)

* Playlist already added song prevention & AndroidSlidingUpPanel repo Update

* Update color for black theme, now playing card to have a black color with some radius

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

@@ -101,6 +101,7 @@
                 android:layout_marginRight="16dp"
                 android:layout_marginTop="8dp"
                 app:cardBackgroundColor="?cardBackgroundColor"
+                sothree:cardCornerRadius="5dp"
                 app:cardElevation="@dimen/card_elevation"
                 app:cardUseCompatPadding="false">
 

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

@@ -10,7 +10,7 @@
     <RelativeLayout
         android:layout_width="match_parent"
         android:layout_height="@dimen/progress_container_height"
-        android:background="@color/twenty_percent_black_overlay">
+        android:background="@android:color/black">
 
         <TextView
             android:id="@+id/player_song_current_progress"

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

@@ -100,6 +100,7 @@
                     android:id="@+id/player_panel_content"
                     android:layout_width="match_parent"
                     android:layout_height="wrap_content"
+                    android:background="?cardBackgroundColor"
                     android:orientation="vertical">
 
                     <View