improve https rewriting

searx/__init__.py

 with open(settings_path) as settings_yaml:
     settings = load(settings_yaml)
 
-# loade https rules
-load_https_rules(https_rewrite_path)
+# load https rules only if https rewrite is enabled
+if settings.get('server', {}).get('https_rewrite'):
+    # loade https rules
+    load_https_rules(https_rewrite_path)

searx/webapp.py

                             # set new url
                             result['url'] = new_result_url
 
+                    # target has matched, do not search over the other rules 
+                    break
+
         if search.request_data.get('format', 'html') == 'html':
             if 'content' in result:
                 result['content'] = highlight_content(result['content'],