Fuzz strategy selection fix (#559)

* added files to compute bandit probabilities as a cron task

* fixed formatting in bandit files

* fixed revisions and renamed some fuzz strategy selection files (previously called bandit probabilities)

* Updated cron.yaml and server.py files. Also updated server SQL query and corresponding tests.

* Got rid of strategy count field in ndb datastore table

* added code to delete previous strategy probability entries upon update

* fixed stylistic errors

* fixed more stylistic errors and updated to use ndb_utils to delete from table

* fixed some naming issues and udpated types.go file to represent new ndb table schema

* fixed bigquery query result bug

src/appengine/handlers/cron/fuzz_strategy_selection.py

@@ -99,7 +99,7 @@ def _query_multi_armed_bandit_probs(client):
 
   Queries above BANDIT_PROBABILITY_QUERY and yields results
   from bigquery. This query is sorted by strategies implemented."""
-  return client.query(query=BANDIT_PROBABILITY_QUERY)
+  return client.query(query=BANDIT_PROBABILITY_QUERY).rows
 
 
 def _query_and_upload_strategy_weights(client):