Simplify test setup for existing experiments.

[ClemensBuechner]

Most of the existing example experiments require a specific version of Fast Downward and/or LP-solver. Checking whether the experiments still run is therefore always a pain. One idea was to add a container bundling the required code and the necessary environment variables which can then be used in the experiment instead of requiring the user to set that up themselves.

Along the way, we should also make sure that all the experiments actually still run through, because we didn't really check that all the time when working towards version 1.0.