Tune Elasticsearch boost config

Reward course runs with enrollable, paid seats. Penalize those without them. Slightly increase boost given to MicroMasters and Professional Certificate programs. Tweak self-paced and enrollable boosts to match. Taken together, this modified boost configuration yields search results which tend to promote course runs with enrollable, paid seats above those without them.

LEARNER-1374

course_discovery/apps/edx_haystack_extensions/backends.py

@@ -36,7 +36,7 @@ class SimpleQuerySearchBackendMixin(object):
             'auto_generate_phrase_queries': True,
         }
 
-        # https://www.elastic.co/guide/en/elasticsearch/reference/1.7/query-dsl-function-score-query.html
+        # https://www.elastic.co/guide/en/elasticsearch/reference/1.5/query-dsl-function-score-query.html
         function_score_config = get_elasticsearch_boost_config()['function_score']
         function_score_config['query'] = {
             'query_string': simple_query

course_discovery/settings/devstack.py

@@ -7,7 +7,6 @@ LOGGING['handlers']['local'] = {
     'class': 'logging.NullHandler',
 }
 
-
 # Determine which requests should render Django Debug Toolbar
 INTERNAL_IPS = ('127.0.0.1',)