Adding mxnet components to rl_coach/architectures (#60)

Adding mxnet components to rl_coach architectures.

- Supports PPO and DQN
- Tested with CartPole_PPO and CarPole_DQN
- Normalizing filters don't work right now (see #49) and are disabled in CartPole_PPO preset
- Checkpointing is disabled for MXNet

rl_coach/architectures/network_wrapper.py

@@ -183,16 +183,7 @@ class NetworkWrapper(object):
                                      target_network or global_network) and the second element is the inputs
         :return: the outputs of all the networks in the same order as the inputs were given
         """
-        feed_dict = {}
-        fetches = []
-
-        for idx, (network, input) in enumerate(network_input_tuples):
-            feed_dict.update(network.create_feed_dict(input))
-            fetches += network.outputs
-
-        outputs = self.sess.run(fetches, feed_dict)
-
-        return outputs
+        return type(self.online_network).parallel_predict(self.sess, network_input_tuples)
 
     def get_local_variables(self):
         """