[enh] add support for yacy engine (localhost)

searx/engines/yacy.py

+from json import loads
+from urllib import urlencode, quote
+
+url = 'http://localhost:8090'
+search_url = '/yacysearch.json?{query}&maximumRecords=10'
+
+def request(query, params):
+    params['url'] = url + search_url.format(query=urlencode({'query':query}))
+    return params
+
+def response(resp):
+    raw_search_results = loads(resp.text)
+    
+    if not len(raw_search_results):
+        return []
+
+    search_results = raw_search_results.get('channels', {})[0].get('items', [])
+
+    results = []
+
+    for result in search_results:
+        tmp_result = {}
+        tmp_result['title'] = result['title']
+        tmp_result['url'] = result['link']
+        tmp_result['content'] = '' 
+        
+        if len(result['description']):
+            tmp_result['content'] += result['description'] +"<br/>" 
+
+        if len(result['pubDate']):
+            tmp_result['content'] += result['pubDate'] + "<br/>"
+
+        if result['size'] != '-1':
+            tmp_result['content'] += result['sizename']
+
+        results.append(tmp_result)
+
+    return results