Fixed inconsistent image names.

The images have been renamed to be more consistent and moved into
the "images" directory to mimic the original jQuery UI structure.

Ticket #1613

install/migration/error.html

@@ -13,7 +13,7 @@
 
   <div class="container_1">
     <div class="header-logo">
-            <img src="../ui/ipalogo.png" /><img src="../ui/ipabanner.png" />
+            <img src="../ui/images/ipa-logo.png" /><img src="../ui/images/ipa-banner.png" />
         </div>
         <br>
         <br>