Improve containerization integration

[jjcollinge]

Currently we do not recommend running Traefik in a container on Service Fabric. This is only because we haven't proven a best practice setup. The current setup is documented here. We can improve upon this by looking to resolve the host IP outside the container and mount it in.

Some potential pitfalls.

• Cleaning up container volumes
• Limited networking modes supported on Windows Server
• Cannot edit Manifests at run time

@askw @flmader

[lawrencegripper]

In order to greatly simplify the setup and deployment of Traefik in a cluster we could look to use a setup script on the host which extracts the necessary pfx and concerts it to the pem and cert files needed for traefik to access the cluster. These can then be mounted into the Traefik container using a host mounting.

The goal would be to allow a user to deploy Traefik into a cluster by simple adding the container image, setupEntryPoint and the thumbprint of the clusters cert.

[jjcollinge]

This could also work with guest executables - just grab the cert, generate the pems and stick them in the code package.

[jjcollinge]

Adding support for CLUSTERMANAGEMENTURL env var to overwrite the .toml configuration. This will allow us to set the clustermanagementurl to the container's gateway when Traefik runs in a container. cc @flmader - TODO: testing on Linux