Fix in documentation - reporter tgeorg-ethz

Closes #342

See merge request !324

rail_env.py: Wrong values for alpha and beta in comment.
The values stated for alpha and beta in flatland/envs/rail_env are stated to be 1 for both in the comment but are 0 in the actual code a few lines below.

Juypter notebook cleaned up

See merge request !323

- unused imports removed
- removed unused code

are no ready for benchmarking

- unused imports removed
- removed unused code

are no ready for benchmarking

- unused imports removed
- removed unused code

- unused imports removed
- removed unused code

But they should be overworked. Might just one example per use case would be much more clear. TODO - cleanup

But they should be overworked. Might just one example per use case would be much more clear. TODO - cleanup

But they should be overworked. Might just one example per use case would be much more clear. TODO - cleanup

But they should be overworked. Might just one example per use case would be much more clear. TODO - cleanup

But they should be overworked. Might just one example per use case would be much more clear. TODO - cleanup

But they should be overworked. Might just one example per use case would be much more clear. TODO - cleanup

But they should be overworked. Might just one example per use case would be much more clear. TODO - cleanup

But they should be overworked. Might just one example per use case would be much more clear. TODO - cleanup

But they should be overworked. Might just one example per use case would be much more clear. TODO - cleanup

But they should be overworked. Might just one example per use case would be much more clear. TODO - cleanup

But they should be overworked. Might just one example per use case would be much more clear. TODO - cleanup

But they should be overworked. Might just one example per use case would be much more clear. TODO - cleanup

But they should be overworked. Might just one example per use case would be much more clear. TODO - cleanup

But they should be overworked. Might just one example per use case would be much more clear. TODO - cleanup

But they should be overworked. Might just one example per use case would be much more clear. TODO - cleanup

But they should be overworked. Might just one example per use case would be much more clear. TODO - cleanup

But they should be overworked. Might just one example per use case would be much more clear. TODO - cleanup

But they should be overworked. Might just one example per use case would be much more clear. TODO - cleanup

But they should be overworked. Might just one example per use case would be much more clear. TODO - cleanup

     - test-notebooks