Load scenarios from git repo

[christophd]

On simulator startup simulator should be able to load a git repo that defines the scenarios.

TODO: Find out how we can load Java scenario code at runtime.

[christophd]

Maybe use Groovy scenario scripts then.

[bbortt]

I think that should be fairly easy, right? loading scenarios at runtime is already supported (we do it based on XML), just not from a GIT repository.

would actually be a cool addition!