Display media description rather than caption for 'Abstract/Description'

Hopefully this will only affect the item display page for WP media, but
it's worth some exploration around other settings to make sure the file
isn't invoked elsewhere.

Part of https://github.com/NEU-DSG/toolkit_requests/issues/120

inc/item.php

@@ -16,7 +16,7 @@ function get_item_details($data, $assoc=false){
   $html = '';
   if ($repo == "wp"){
     $abs = "Abstract/Description";
-    $data->mods->$abs = $data->post_excerpt;
+    $data->mods->$abs = $data->post_content;
     $datec = "Date created";
     $data->mods->$datec = $data->post_date;
   }