Give Layers Access to docker-host filesystem

[amdfxlucas]

Sometimes Layers need to generate files on the docker-host itself, rather than on node's/container's file system.
I.e. to use the CA/Web-Services with the browser a small helper script is required to install the RootCAStore's CAcertificate into the browsers trust store. The script should be located in the output directory, next to the docker-compose.yml, which is unknown at the time of configure() (only by the Docker compiler). So as of now the directory has to be hardcoded or the script shipped with each example (duplication).

In this particular case one could argue to just make the script a 'tool' like the blockchain wallet and etherview, but the described feature could benefit other Layers and use cases as well.