Merge branch 'master' of gitlab.aicrowd.com:adrian_egli/neurips2020-flatland-starter-kit into feature/DeadLockAvoidance_RL_PostChallenge

# Conflicts:
#	.gitignore
#	README.md
#	aicrowd.json
#	apt.txt
#	environment.yml
#	my_observation_builder.py
#	reinforcement_learning/dddqn_policy.py
#	reinforcement_learning/evaluate_agent.py
#	reinforcement_learning/model.py
#	reinforcement_learning/multi_agent_training.py
#	reinforcement_learning/ordered_policy.py
#	reinforcement_learning/policy.py
#	reinforcement_learning/ppo/ppo_agent.py
#	reinforcement_learning/single_agent_training.py
#	run.py
#	utils/dead_lock_avoidance_agent.py
#	utils/deadlock_check.py
#	utils/observation_utils.py
#	utils/timer.py