Support multi-port service routing for containers running on Marathon

[aantono]

Similar to requirements in #444, provide Marathon support to match the following requirements:

If labels contain for example:

traefik.mycustomservice.port=443
traefik.mycustomservice.frontend.rule=Path:/mycustomservice
traefik.anothercustomservice.port=8080
traefik.anothercustomservice.frontend.rule=Path:/anotherservice

all traffic to frontend on path /mycustomservice is redirected to the port 443 of the container defining the label while using path /anotherservice will redirect to the port 8080 of the docker container defining the label

Available properties are

traefik.<service-name>.port
traefik.<service-name>.weight
traefik.<service-name>.protocol
traefik.<service-name>.frontend.backend
traefik.<service-name>.frontend.entryPoints
traefik.<service-name>.frontend.rule
traefik.<service-name>.frontend.passHostHeader
traefik.<service-name>.frontend.priority
traefik.<service-name>.frontend.rule

[aantono]

Closing due to #1701 being merged to master