Fixing bugs branch

[DominikRoB]

A few fixes for bugs, which lead to crashes.

Add functionality to set seed for random number generator

Copied some changes from the latest commits, but in smaller steps.

Ignored changes for RLLib (Like the EnvContext), because it adds Ray as Dependency to the environment. This would force others to use Ray, too. If you plan to keep them, note that the path to the instances from the configs are incorrectly handled.

Made sure all tests passed right before the pull request. (Using Python 3.9 on Windows, using Anaconda)

[PhilippWillms]

Any update on those topics?