Added single agent global obs

experiments/flatland_single/small_single_v0/global_obs_conv_net/ppo.yaml

+flatland-sparse-single-global-conv-ppo:
+    run: PPO
+    env: flatland_single
+    stop:
+        timesteps_total: 10000000  # 1e7
+    checkpoint_freq: 10
+    checkpoint_at_end: True
+    keep_checkpoints_num: 5
+    checkpoint_score_attr: episode_reward_mean
+    config:
+        clip_rewards: True
+        clip_param: 0.1
+        vf_clip_param: 500.0
+        entropy_coeff: 0.01
+        # effective batch_size: train_batch_size * num_agents_in_each_environment [5, 10]
+        # see https://github.com/ray-project/ray/issues/4628
+        train_batch_size: 1000  # 5000
+        rollout_fragment_length: 50  # 100
+        sgd_minibatch_size: 100  # 500
+        num_sgd_iter: 10
+        num_workers: 11
+        num_envs_per_worker: 5
+        batch_mode: truncate_episodes
+        observation_filter: NoFilter
+        vf_share_layers: True
+        vf_loss_coeff: 0.5
+        num_gpus: 1
+
+        env_config:
+            observation: global
+            observation_config:
+                max_width: 32
+                max_height: 32
+
+            generator: sparse_rail_generator
+            generator_config: small_single_v0
+
+            wandb:
+                project: flatland
+                entity: masterscrat
+                tags: ["small_single_v0", "global_obs"] # TODO should be set programmatically
+
+        model:
+            custom_model: global_obs_model
+            custom_options:
+                architecture: impala
+                architecture_options:
+                    residual_layers: [[16, 2], [32, 4]]