Option to switch off album art or to prefer file over embedded

Large embedded album art can cause pauses during
playback or when skipping between tracks, especially
on older devices, but embedded art is currently loaded
even when separately stored smaller image files would be
available.

A workaround is to remove large album art from the
metadata of files.

This now adds a setting to either turn off loading of
album art completely, or to prefer loading the album art
from a separate image file and thus ignore the embedded
versions.

Change-Id: I22fb581abf56072e35e6c29d72e553747ec1a96a

apps/gui/quickscreen.c

@@ -39,6 +39,9 @@
 #include "option_select.h"
 #include "debug.h"
 #include "shortcuts.h"
+#ifdef HAVE_ALBUMART
+#include "playback.h"
+#endif
 
  /* 1 top, 1 bottom, 2 on either side, 1 for the icons
   * if enough space, top and bottom have 2 lines */
@@ -411,6 +414,9 @@ int quick_screen_quick(int button_enter)
     struct gui_quickscreen qs;
     bool oldshuffle = global_settings.playlist_shuffle;
     int oldrepeat = global_settings.repeat_mode;
+#ifdef HAVE_ALBUMART
+    int old_album_art = global_settings.album_art;
+#endif
     bool usb = false;
 
     if (global_settings.shortcuts_replaces_qs)
@@ -446,6 +452,10 @@ int quick_screen_quick(int button_enter)
             else
                 playlist_sort(NULL, true);
         }
+#ifdef HAVE_ALBUMART
+        if (old_album_art != global_settings.album_art)
+            set_albumart_mode(global_settings.album_art);
+#endif
     }
     return (usb ? 1:0);
 }