Command: Fablo connect to join existing cluster / instance of the network

[dzikowski]

Probably a good PoC of the feature is to support the following scenario:

1. In the directory ./network1 start a fablo network (fablo init && fablo up)
2. In the another directory: ./network2:
   a. Prepare fablo-config.json with single peer from Org1 (the same org as in network1), and a reference to CA (?), certs (?), whatever is required to access another network. We need to determine the structure of the new file and what information is required.
   b. Run fablo up.
   c. The second network starts a peer which joins the ./network1, channels.

Ultimately we should be able to join a peer, orderer, maybe even run chaincodes. But for a start supporting just the peer is sufficient.

The ./network/fablo-config.json file may look as follows:

{
  "$schema": "https://github.com/hyperledger-labs/fablo/releases/download/2.4.3/schema.json",
  "global": {
    "fabricVersion": "3.1.0",
    "tls": true
  },
  "orgs": [
    {
      "organization": {
        "name": "Org1",
        "domain": "org1.example.com",
        "mspName": "Org1MSP"
      },
      "ca": {
        "url": "...",
        "tlsCACertPath": "..."
      },
      "peer": {
        "instances": 1
      }
    }
  ],
  "channels": [
    {
      "name": "my-channel1",
      "orgs": [
        {
          "name": "Org1",
          "peers": [
            "peer0"
          ]
        }
      ]
    }
  ]
}