tokenising marathon JSON files

[sadovnikov]

Not ready just YET. Tests should be changed too

[sadovnikov]

Done. These changes enable installation of Marathon app with tokens in JSON. For example,

{
  "id": "hello-world-scheduler",
  "cmd": "docker run containersol/mesos-hello-world-scheduler --mesosMaster ${MINIMESOS_MASTER_IP}:${MINIMESOS_MASTER_PORT}",
  "cpus": 0.2,
  "mem": 512.0,
  "env": {
    "JAVA_OPTS": "-Xms128m -Xmx256m"
  },
  "instances": 1
}

Supports ${MINIMESOS_[ROLE]}, ${MINIMESOS_[ROLE]_IP} and ${MINIMESOS_[ROLE]_PORT tokens, where [ROLE] is the container role in the cluster: ZOOKEEPER, MARATHON, CONSUL, MASTER

[frankscholten]

LGTM