[enh] bing, google paging support

searx/engines/bing.py

 from cgi import escape
 
 base_url = 'http://www.bing.com/'
-search_string = 'search?{query}'
+search_string = 'search?{query}&first={offset}'
 locale = 'en-US'  # see http://msdn.microsoft.com/en-us/library/dd251064.aspx
 
+paging = True
+
 
 def request(query, params):
+    offset = (params['pageno'] - 1) * 10 + 1
     search_path = search_string.format(
-        query=urlencode({'q': query, 'setmkt': locale}))
+        query=urlencode({'q': query, 'setmkt': locale}),
+        offset=offset)
     #if params['category'] == 'images':
     #    params['url'] = base_url + 'images/' + search_path
     params['url'] = base_url + search_path

searx/engines/google.py

 
 categories = ['general']
 
+paging = True
+
 url = 'https://ajax.googleapis.com/'
-search_url = url + 'ajax/services/search/web?v=1.0&start=0&rsz=large&safe=off&filter=off&{query}'  # noqa
+search_url = url + 'ajax/services/search/web?v=1.0&start={offset}&rsz=large&safe=off&filter=off&{query}'  # noqa
 
 
 def request(query, params):
-    params['url'] = search_url.format(query=urlencode({'q': query}))
+    offset = (params['pageno'] - 1) * 8
+    params['url'] = search_url.format(offset=offset,
+                                      query=urlencode({'q': query}))
     return params