Basic ajax error handling.

Provide a placeholder for ajax errors and just ask user to reload page when
such error happens.

During each ajax communication starts cleanup the handler, in order to have it
empty in case if next request was successful.

master/bt5/vifib_web/SkinTemplateItem/portal_skins/vifib_hosting/WebSection_viewSoftwareRender.xml

@@ -49,7 +49,11 @@
 <div id="js_container"></div>\n
 <script type="text/javascript">\n
 $(document).ready(function() {\n
-  $.ajaxSetup ({cache: false});\n
+  $(document).ajaxStart(cleanAjaxError);\n
+  $.ajaxSetup ({\n
+    cache: false,\n
+    error: processAjaxError\n
+  });\n
   $.getJSON(vifib[\'site_url\'] + "/ERP5Site_getSoftwareCategoryTreeAsJSON", drawSoftwareCategoryTree);\n
   $(window).hashchange(hashController);\n
   $(window).hashchange();\n

master/bt5/vifib_web/SkinTemplateItem/portal_skins/vifib_hosting_theme/vifib_hosting_js/vifib.js.xml

@@ -8,7 +8,7 @@
       <dictionary>
         <item>
             <key> <string>_EtagSupport__etag</string> </key>
-            <value> <string>ts23190925.51</string> </value>
+            <value> <string>ts23256173.14</string> </value>
         </item>
         <item>
             <key> <string>__name__</string> </key>
@@ -484,7 +484,24 @@ function hashController() {\n
       softwareReleaseController(query, query_kw.software_category, page)\n
   }\n
 }\n
-
+\n
+function cleanAjaxError(data, textStatus, jqXHR) {\n
+  ajax_error = $(\'#ajax_error\');\n
+  if (ajax_error.length > 0) {\n
+    ajax_error.empty();\n
+  }\n
+}\n
+\n
+function processAjaxError(jqXHR, textStatus, errorThrown) {\n
+  ajax_error = $(\'#ajax_error\');\n
+  if (ajax_error.length == 0) {\n
+    container = $(\'#js_container\');\n
+    ajax_error = $(\'<div>\').addClass(\'error\').attr(\'id\', \'ajax_error\');\n
+    container.before(ajax_error);\n
+  }\n
+  ajax_error.empty()\n
+  ajax_error.html(\'There was issue with server communication. Please try to reload the page.\');\n
+}
 
 ]]></string> </value>
         </item>
@@ -494,7 +511,7 @@ function hashController() {\n
         </item>
         <item>
             <key> <string>size</string> </key>
-            <value> <int>15833</int> </value>
+            <value> <int>16369</int> </value>
         </item>
         <item>
             <key> <string>title</string> </key>