[enh][mod] result handling refactor

Several changes has been made:
 - Parallel result merge
 - Scoring algorithm slightly changed (see result_score())
 - Proper Thread locking on global data manipulation

searx/tests/test_results.py

@@ -0,0 +1,41 @@
+# -*- coding: utf-8 -*-
+
+from searx.results import ResultContainer
+from searx.testing import SearxTestCase
+
+
+def fake_result(url='https://aa.bb/cc?dd=ee#ff',
+                title='aaa',
+                content='bbb',
+                engine='wikipedia', **kwargs):
+    result = {'url': url,
+              'title': title,
+              'content': content,
+              'engine': engine}
+    result.update(kwargs)
+    return result
+
+
+#  TODO
+class ResultContainerTestCase(SearxTestCase):
+
+    def test_empty(self):
+        c = ResultContainer()
+        self.assertEqual(c.get_ordered_results(), [])
+
+    def test_one_result(self):
+        c = ResultContainer()
+        c.extend('wikipedia', [fake_result()])
+        self.assertEqual(c.results_length(), 1)
+
+    def test_one_suggestion(self):
+        c = ResultContainer()
+        c.extend('wikipedia', [fake_result(suggestion=True)])
+        self.assertEqual(len(c.suggestions), 1)
+        self.assertEqual(c.results_length(), 0)
+
+    def test_result_merge(self):
+        c = ResultContainer()
+        c.extend('wikipedia', [fake_result()])
+        c.extend('wikidata', [fake_result(), fake_result(url='https://example.com/')])
+        self.assertEqual(c.results_length(), 2)