Remove initialization of swarm but display useful error

[NicolasMahe]

Closes #213

This PR remove the initialization of swarm from the container package, and display a useful error instead.

Example from a digital ocean droplet:

root@test-swarm-2:~# mesg-core
Docker Swarm is not initialized. Execute "docker swarm init" and try again

root@test-swarm-2:~# docker swarm init
Error response from daemon: could not choose an IP address to advertise since this system has multiple addresses on interface eth0 (128.199.243.244 and 10.15.0.8) - specify one with --advertise-addr

root@test-swarm-2:~# docker swarm init --advertise-addr 128.199.243.244
Swarm initialized: current node (sng5snnh5cm46yibdsz7bevq8) is now a manager.

To add a worker to this swarm, run the following command:

    docker swarm join --token SWMTKN-1-0kzu7i28acwa3pl0c5nsll7wo0z2xgb0pql54wlez70uwnybea-6d3kowvsni0oqztuxc7z3v2w9 128.199.243.244:2377

To add a manager to this swarm, run 'docker swarm join-token manager' and follow the instructions.

root@test-swarm-2:~# mesg-core
MESG Core dev build test-swarm

Usage:
  mesg-core [command]

Available Commands:
  help        Help about any command
  logs        Show the Core's logs
  service     Manage services
  start       Start the Core
  status      Get the Core's status
  stop        Stop the Core

Flags:
  -h, --help         help for mesg-core
      --no-color     disable colorized output
      --no-spinner   disable spinners
      --version      version for mesg-core

Use "mesg-core [command] --help" for more information about a command.
root@test-swarm-2:~#