Enabling-more-agents-for-Batch-RL-and-cleanup (#258)

allowing for the last training batch drawn to be smaller than batch_size + adding support for more agents in BatchRL by adding softmax with temperature to the corresponding heads + adding a CartPole_QR_DQN preset with a golden test + cleanups

rl_coach/agents/dqn_agent.py

@@ -86,7 +86,7 @@ class DQNAgent(ValueOptimizationAgent):
 
         #  only update the action that we have actually done in this transition
         TD_errors = []
-        for i in range(self.ap.network_wrappers['main'].batch_size):
+        for i in range(batch.size):
             new_target = batch.rewards()[i] +\
                          (1.0 - batch.game_overs()[i]) * self.ap.algorithm.discount * np.max(q_st_plus_1[i], 0)
             TD_errors.append(np.abs(new_target - TD_targets[i, batch.actions()[i]]))