Make markets and blockchains customizable by adding a config file

[Jonathan Gros-Dubois]

Proposed format (example):

{
  "blockchains": {
    "clsk": {
      "name": "Capitalisk",
      "apiURL": "http://111.111.111.111:7010/api"
    },
    "lsh": {
      "name": "Leasehold",
      "apiURL": "http://222.222.222.222:7020/api"
    },
    "lsk": {
      "name": "Lisk",
      "apiURL": "https://test-02.liskapi.io/api"
    }
  },
  "markets": {
    "CLSK/LSK": {
      "description": "Capitalisk testnet DEX market",
      "apiURL": "http://12.12.12.12:7011",
      "baseChain": {
        "symbol": "lsk",
        "address": "11179270540263472691L"
      },
      "quoteChain": {
        "symbol": "clsk",
        "address": "6654385933994690090L"
      }
    },
    "LSH/LSK": {
      "description": "Leasehold testnet DEX market",
      "apiURL": "http://33.33.33.33:7011",
      "baseChain": {
        "symbol": "lsk",
        "address": "3330447115707170931L"
      },
      "quoteChain": {
        "symbol": "lsh",
        "address": "11196650803908033515L"
      }
    }
  }
}