Add RedisDataStore (#295)

* GraphManager.set_session also sets self.sess

* make sure that GraphManager.fetch_from_worker uses training phase

* remove unnecessary phase setting in training worker

* reorganize rollout worker

* provide default name to GlobalVariableSaver.__init__ since it isn't really used anyway

* allow dividing TrainingSteps and EnvironmentSteps

* add timestamps to the log

* added redis data store

* conflict merge fix

rl_coach/architectures/tensorflow_components/savers.py

@@ -24,7 +24,7 @@ from rl_coach.saver import Saver
 
 
 class GlobalVariableSaver(Saver):
-    def __init__(self, name):
+    def __init__(self, name=""):
         self._names = [name]
         # if graph is finalized, savers must have already already been added. This happens
         # in the case of a MonitoredSession