Added option to switch themes.

Added standalone pages for:
 - Exhibitions
 - Events
 - Institutions
 - Collections
Added option to limit display to only a given set of institutions.

edit/page.php

@@ -57,12 +57,13 @@ if (isset($task)) {
 
     else if ($task == "delete") {
 
-        if (isset($id)) {
+        if (!isset($id)) {
             echo printErrorPage($translations['specifyToDelete']); return;
         }
 
         unlink(__DIR__ . "/../data/static/$id.json");
         generateStaticPgCaches();
+        header('Location: pages.php');
     }
 
 }