Add an No Api Flickr Engine

It uses the webpage json infos to build the results
Let the user choose the engine in setting.yml. Noapi active by default
+ little corrections on Flickr engine

searx/settings.yml

@@ -65,12 +65,15 @@ engines:
 #    categories : files
 #    shortcut : fc
 
-# api-key required: https://www.flickr.com/services/apps/create/
-#  - name : flickr
+  - name : flickr
+    categories : images
+    shortcut : fl
+# You can use the engine using the official stable API, but you need an API key
+# See : https://www.flickr.com/services/apps/create/
 #    engine : flickr
-#    categories : images
-#    shortcut : fl
 #    api_key: 'apikey' # required!
+# Or you can use the html non-stable engine, activated by default
+    engine : flickr-noapi
 
   - name : general-file
     engine : generalfile