Fix cmd line arguments handling (#68)

* refactoring the merging of the task parameters and the command line parameters
* removing some unused command line arguments
* fix for saving checkpoints when not passing through coach.py

rl_coach/architectures/tensorflow_components/distributed_tf_utils.py

@@ -94,7 +94,7 @@ def create_monitored_session(target: tf.train.Server, task_index: int,
         is_chief=is_chief,
         hooks=[],
         checkpoint_dir=checkpoint_dir,
-        checkpoint_save_secs=checkpoint_save_secs,
+        save_checkpoint_secs=checkpoint_save_secs,
         config=config
     )