Implement support for listing clones sessions and multicast groups

[tatry]

Closes #24

Example JSON:

• List of all clone sessions:

  {
    "clone_sessions": [
        {
            "id": 8,
            "entries": [
                {
                    "port": 6,
                    "instance": 2,
                    "class_of_service": 1,
                    "truncate": false
                },
                {
                    "port": 6,
                    "instance": 1,
                    "class_of_service": 0,
                    "truncate": false
                }
            ]
        },
        {
            "id": 10,
            "entries": [
                {
                    "port": 7,
                    "instance": 25,
                    "class_of_service": 0,
                    "truncate": true,
                    "truncate_length": 1200
                }
            ]
        }
    ]
  }

• List of all multicast groups:

  {
    "multicast_groups": [
        {
            "id": 8,
            "members": [
                {
                    "port": 6,
                    "instance": 1
                },
                {
                    "port": 5,
                    "instance": 1
                }
            ]
        },
        {
            "id": 10,
            "members": [
                {
                    "port": 7,
                    "instance": 20
                }
            ]
        }
    ]
  }