Add weighted averages report

[ZIMkaRU]

This PR adds the weighted averages report https://www.investopedia.com/terms/w/weightedaverage.asp. The idea is to select a time period for trades and calculates for each specific pair:

• Buy
  • Weighted average buying price (Only sum up buying trades)
  • Amount bought (Only sum up buying trades)
• Sell
  • Weighted average Selling price (Only sum up selling trades)
  • Amount Sold (Only sum up selling trades)
• Cumulative
  • Weighted average price (Both buy and sell trades)
  • Final amount (Amount bought - amount sold)

---

Basic changes:

• Adds getWeightedAveragesReport method to the main service
• Adds getWeightedAveragesReportCsv method to the main service
• Adds corresponding test coverage

---

Request example:

{
  "auth": {
    "token": "the-user-token"
  },
  "method": "getWeightedAveragesReport",
  "params": {
    // "symbol": ["tIOTUSD", "tETHUSD"] - we can pass array of pairs for filtering, or skip it param if no necessary
    "start": 1576339450000,
    "end": 1576521468000
  }
}

Response example:

{
  "jsonrpc": "2.0",
  "result": [
    {
      "symbol": "tNEOUSD",
      "buyingWeightedPrice": 8.311941599594718,
      "buyingAmount": 6.70696301,
      "sellingWeightedPrice": 0,
      "sellingAmount": 0,
      "cumulativeWeightedPrice": 8.311941599594718,
      "cumulativeAmount": 6.70696301
    },
    {
      "symbol": "tXRPUSD",
      "buyingWeightedPrice": 0.2119784948940276,
      "buyingAmount": 52.18668382,
      "sellingWeightedPrice": 0.21406,
      "sellingAmount": -25.78324287,
      "cumulativeWeightedPrice": 0.2099458828650097,
      "cumulativeAmount": 26.403440950000004
    },
    {
      "symbol": "tIOTUSD",
      "buyingWeightedPrice": 0.18546723624755995,
      "buyingAmount": 203.9278243,
      "sellingWeightedPrice": 0.18711,
      "sellingAmount": -101.45977508,
      "cumulativeWeightedPrice": 0.18384063710664833,
      "cumulativeAmount": 102.46804922
    },
    {
      "symbol": "tETHUSD",
      "buyingWeightedPrice": 139.93966231409323,
      "buyingAmount": 0.29878416,
      "sellingWeightedPrice": 0,
      "sellingAmount": 0,
      "cumulativeWeightedPrice": 139.93966231409323,
      "cumulativeAmount": 0.29878416
    }
  ],
  "id": null
}

Request example:

{
  "auth": {
    "token": "the-user-token"
  },
  "method": "getMultipleCsv",
  "params": {
    "language": "en",
    "multiExport": [
      {
        "symbol": ["tIOTUSD", "tETHUSD"],
        "start": 1576339450000,
        "end": 1576521468000,
        "timezone": "Etc/UTC",
        "dateFormat": "DD-MM-YY",
        "milliseconds": false,
        "method": "getWeightedAveragesReportCsv"
      }
    ]
  }
}

Response example:

{
  "jsonrpc": "2.0",
  "result": {
    "isSaveLocaly": true,
    "localCsvFolderPath": "/home/vladimir/projects/bitfinex/bfx-reports-framework/csv",
    "remoteCsvUrn": null
  },
  "id": null
}

---

CSV example:

[ezewer]

looks good to me!