Disable engine by default.

searx/settings.yml

@@ -300,11 +300,13 @@ engines:
     engine : vimeo
     shortcut : vm
 
-  - name : wolframalpha
-    shortcut : wa
-    engine : wolframalpha_api
-    api_key: '5952JX-X52L3VKWT8'
-    timeout: 6.0
+# You can use the engine using the official stable API, but you need an API key
+# See : http://products.wolframalpha.com/api/
+#  - name : wolframalpha
+#    shortcut : wa
+#    engine : wolframalpha_api
+#    api_key: 'apikey' # required!
+#    timeout: 6.0
 
 #The blekko technology and team have joined IBM Watson! -> https://blekko.com/
 #  - name : blekko images