erp5_web_renderjs_ui: Make WebSite.description and WebSite.keywords available for WebPages

To make basic support for search engines ``description`` and ``keywords``

/reviewed-on !253

bt5/erp5_web_renderjs_ui/PathTemplateItem/web_page_module/rjs_gadget_erp5_launcher_html.html

@@ -6,7 +6,8 @@
     <link rel="shortcut icon" href="favicon.ico">
 
     <title>${application_title}</title>
-
+    <meta name="description" content="${site_description}">
+    <meta name="keywords" content="${site_keywords}">
     <link rel="stylesheet" href="gadget_erp5_nojqm.css">
 
     <script data-renderjs-configuration="application_title" type="text/x-renderjs-configuration">${application_title}</script>

bt5/erp5_web_renderjs_ui/PathTemplateItem/web_page_module/rjs_gadget_erp5_launcher_html.xml

@@ -236,7 +236,7 @@
             </item>
             <item>
                 <key> <string>serial</string> </key>
-                <value> <string>956.14408.38027.58965</string> </value>
+                <value> <string>958.32778.10430.62549</string> </value>
             </item>
             <item>
                 <key> <string>state</string> </key>
@@ -254,7 +254,7 @@
                     </tuple>
                     <state>
                       <tuple>
-                        <float>1482764698.23</float>
+                        <float>1491475425.69</float>
                         <string>UTC</string>
                       </tuple>
                     </state>

bt5/erp5_web_renderjs_ui/SkinTemplateItem/portal_skins/erp5_web_renderjs_ui/WebSection_renderDefaultPageAsGadget.py

@@ -41,4 +41,6 @@ return default_web_page.WebPage_viewAsWeb(mapping_dict={
   "language_map": json.dumps({tmp['id']: portal.Base_translateString(tmp['title'], lang = tmp['id']) for tmp in portal.Localizer.get_languages_map() if tmp['id'] in available_language_set}),
   "default_selected_language":  portal.Localizer.get_selected_language(),
   "website_url_set": json.dumps(website_url_set),
+  "site_description": web_section.getLayoutProperty("description", default=""),
+  "site_keywords": web_section.getLayoutProperty("subject", default=""),
 })