PictureFlow: Add 'Track Info' for tracks or whole albums

Context menu gains new option to view
metadata for individual tracks or albums.

Will display an album's length and total file size.
Other fields are displayed only if they are identical
across all tracks (except for the album year, which
is determined by the highest value encountered).

Change-Id: Ibc14cfaf2cb3d91b8d1cfbee05c6261db4975355

apps/plugin.c

@@ -821,6 +821,9 @@ static const struct plugin_api rockbox_api = {
 
     /* new stuff at the end, sort into place next time
        the API gets incompatible */
+
+    splash_progress,
+    splash_progress_set_delay,
 };
 
 static int plugin_buffer_handle;