added realistic_mode for less random levels

added more complex intersections
2 jobs for 147_new_level_generator in 60 minutes (queued for 26 seconds)
Name Stage Failure
failed
tests Tests The script exceeded the maximum execution time set for the job
platform linux -- Python 3.6.7, pytest-5.1.0, py-1.8.0, pluggy-0.12.0
cachedir: .tox/py36/.pytest_cache
rootdir: /builds/flatland/flatland, inifile: setup.cfg
collected 28 items

../../../../tests/test_distance_map.py . [ 3%]
../../../../tests/test_flatland_core_transition_map.py .. [ 10%]
../../../../tests/test_flatland_core_transitions.py ....... [ 35%]
../../../../tests/test_flatland_env_sparse_rail_generator.py .
ERROR: Job failed: execution took longer than 1h0m0s seconds