Batch the backtest with variation in parameters, result in CSV (new pull request from develop branch)

[pprados]

• What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)
  This extension launch many times a back test, with different parameters.
  All the results are added in a CSV file. It's easy to try different parameters values for the same data, or
  to check a strategy in a sliding windows.
  See config.lab in sample-config.js
  To start, check the backtest
  node gekko --config <...> --backtest
  then use
  node labgekko --config <...> --backtest

config.lab={
  enabled:true,
  file:"labs/"+config.tradingAdvisor.method+".csv",
  // Fields to add in CSV. Can be omitted or reorders
  fields:[
    "method", "exchange","currency","asset",
    "candleSize","historySize",
    "patchs",
    "startTime","endTime","timespan",
    "startPrice","endPrice","market","trades",
    "startBalance","balance","profit",
    "relativeProfit", "relativeResult"
  ],
  // Lists of modification to apply in config.
  patchs:[
    { 
      path: "MACD.short",
      loop: ["5", "<= 15", "+ 5"], // Normal:10
    },
    { 
      path: "MACD.long",
      loop: ["16", "<= 26", "+ 5"], // Normal:21
    },
    { 
      path: "MACD.signal",
      loop: ["8", "<= 10", "+ 1"], // Normal:9
    },
    {
      path:"backtest.daterange",
      exloop:[
        'config.{}={from:"2016-01-01", to: "2016-04-01"}',
        'moment(config.{}.to).isBefore("2017-12-15")',
        'slidingWindow(config.{},1, "month")',
        '// require nothing in global scope',
      ],
    },
  ],
}

• What is the current behavior? (You can also link to an open issue here)

• What is the new behavior (if this is a feature change)?

• Other information:

[pangoyal]

@askmike do you have plans to merge this PR anytime soon?

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions. If you feel this is very a important issue please reach out the maintainer of this project directly via e-mail: gekko at mvr dot me.