fix youtube engine and add comments

* add language-support
* decrease search-results/site to 5
* add comments

searx/engines/youtube.py

+## Youtube (Videos)
+# 
+# @website     https://www.youtube.com/
+# @provide-api yes (http://gdata-samples-youtube-search-py.appspot.com/)
+# 
+# @using-api   yes
+# @results     JSON
+# @stable      yes
+# @parse       url, title, content, publishedDate, thumbnail
+
 from json import loads
 from urllib import urlencode
 from dateutil import parser
 
+# engine dependent config
 categories = ['videos']
-
-search_url = ('https://gdata.youtube.com/feeds/api/videos'
-              '?alt=json&{query}&start-index={index}&max-results=25')  # noqa
-
 paging = True
+language_support = True
+
+# search-url
+base_url = 'https://gdata.youtube.com/feeds/api/videos'
+search_url = base_url + '?alt=json&{query}&start-index={index}&max-results=5'  # noqa
 
 
+# do search-request
 def request(query, params):
-    index = (params['pageno'] - 1) * 25 + 1
+    index = (params['pageno'] - 1) * 5 + 1
+
     params['url'] = search_url.format(query=urlencode({'q': query}),
                                       index=index)
+
+    # add language tag if specified
+    if params['language'] != 'all':
+        params['url'] += '&lr=' + params['language'].split('_')[0]
+
     return params
 
 
+# get response from search-request
 def response(resp):
     results = []
+
     search_results = loads(resp.text)
+
+    # return empty array if there are no results
     if not 'feed' in search_results:
-        return results
+        return []
+
     feed = search_results['feed']
 
+    # parse results
     for result in feed['entry']:
         url = [x['href'] for x in result['link'] if x['type'] == 'text/html']
+
         if not url:
             return
+
         # remove tracking
         url = url[0].replace('feature=youtube_gdata', '')
         if url.endswith('&'):
             url = url[:-1]
+
         title = result['title']['$t']
         content = ''
         thumbnail = ''
 
-#"2013-12-31T15:22:51.000Z"
         pubdate = result['published']['$t']
         publishedDate = parser.parse(pubdate)
 
         else:
             content = result['content']['$t']
 
+        # append result
         results.append({'url': url,
                         'title': title,
                         'content': content,
                         'publishedDate': publishedDate,
                         'thumbnail': thumbnail})
 
+    # return results
     return results

searx/settings.yml

 
   - name : youtube
     engine : youtube
-    categories : videos
     shortcut : yt
 
   - name : dailymotion
     engine : dailymotion
-    locale : en_US
-    categories : videos
     shortcut : dm
 
   - name : vimeo