ZB fetchBalance
ZB fetchBalance

Added margin functionality to fetchBalance:

Isolated:
```
zb.fetchBalance ()
2022-03-09T06:36:40.737Z iteration 0 passed in 341 ms

{
  info: {
    code: '1000',
    message: {
      des: 'success',
      isSuc: true,
      datas: {
        leverPerm: true,
        levers: [
          {
            cNetUSD: '0.00',
            repayLeverShow: '-',
            cCanLoanIn: '0.001975670000000',
            fNetCNY: '146.01687992',
            fLoanIn: '0.00',
            repayLevel: '0',
            level: '1',
            netConvertCNY: '146.016879921549',
            cFreeze: '0.00',
            cUnitTag: 'BTC',
            version: '1646805723199',
            cAvailableUSD: '0.00',
            cNetCNY: '0.00',
            riskRate: '-',
            fAvailableUSD: '20.49273433',
            fNetUSD: '20.49273432',
            cShowName: 'BTC',
            leverMultiple: '5.00',
            couldTransferOutFiat: '20.49273433',
            noticeLine: '1.13',
            fFreeze: '0.00',
            cUnitDecimal: '8',
            fCanLoanIn: '81.970937320000000',
            cAvailable: '0.00',
            repayLock: false,
            status: '1',
            forbidType: '0',
            totalConvertCNY: '146.016879921549',
            cAvailableCNY: '0.00',
            unwindPrice: '0.00',
            fOverdraft: '0.00',
            fShowName: 'USDT',
            statusShow: '%E6%AD%A3%E5%B8%B8',
            cOverdraft: '0.00',
            netConvertUSD: '20.49273433',
            cNetBtc: '0.00',
            loanInConvertCNY: '0.00',
            fAvailableCNY: '146.016879921549',
            key: 'btcusdt',
            fNetBtc: '0.00049387',
            fUnitDecimal: '8',
            loanInConvertUSD: '0.00',
            showName: 'BTC/USDT',
            startLine: '1.25',
            totalConvertUSD: '20.49273433',
            couldTransferOutCoin: '0.00',
            cEnName: 'BTC',
            leverMultipleInterest: '3.00',
            fAvailable: '20.49273433',
            fEnName: 'USDT',
            forceRepayLine: '1.08',
            cLoanIn: '0.00'
          }
        ]
      }
    }
  },
  USDT: { free: 20.49273433, used: 0, total: 20.49273433 },
  free: { USDT: 20.49273433 },
  used: { USDT: 0 },
  total: { USDT: 20.49273433 }
}
```

Cross:
```
zb.fetchBalance ()
2022-03-09T06:39:09.679Z iteration 0 passed in 415 ms

{
  info: {
    code: '1000',
    message: '操作成功',
    result: {
      loanIn: '0',
      total: '71.223',
      riskRate: '-',
      list: [
        {
          fundType: '2',
          loanIn: '0',
          amount: '0',
          freeze: '0',
          overdraft: '0',
          key: 'BTC',
          canTransferOut: '0'
        },
        {
          fundType: '3',
          loanIn: '0',
          amount: '0',
          freeze: '0',
          overdraft: '0',
          key: 'LTC',
          canTransferOut: '0'
        },
        {
          fundType: '99',
          loanIn: '0',
          amount: '0',
          freeze: '0',
          overdraft: '0',
          key: 'TRX',
          canTransferOut: '0'
        },
        {
          fundType: '5',
          loanIn: '0',
          amount: '0',
          freeze: '0',
          overdraft: '0',
          key: 'ETH',
          canTransferOut: '0'
        },
        {
          fundType: '165',
          loanIn: '0',
          amount: '0',
          freeze: '0',
          overdraft: '0',
          key: 'FIL',
          canTransferOut: '0'
        },
        {
          fundType: '134',
          loanIn: '0',
          amount: '0',
          freeze: '0',
          overdraft: '0',
          key: 'DOT',
          canTransferOut: '0'
        },
        {
          fundType: '7',
          loanIn: '0',
          amount: '0',
          freeze: '0',
          overdraft: '0',
          key: 'ETC',
          canTransferOut: '0'
        },
        {
          fundType: '9',
          loanIn: '0',
          amount: '0',
          freeze: '0',
          overdraft: '0',
          key: 'EOS',
          canTransferOut: '0'
        },
        {
          fundType: '11',
          loanIn: '0',
          amount: '0',
          freeze: '0',
          overdraft: '0',
          key: 'QTUM',
          canTransferOut: '0'
        },
        {
          fundType: '13',
          loanIn: '0',
          amount: '10',
          freeze: '0',
          overdraft: '0',
          key: 'USDT',
          canTransferOut: '10'
        },
        {
          fundType: '14',
          loanIn: '0',
          amount: '0',
          freeze: '0',
          overdraft: '0',
          key: 'XRP',
          canTransferOut: '0'
        },
        {
          fundType: '15',
          loanIn: '0',
          amount: '0',
          freeze: '0',
          overdraft: '0',
          key: 'QC',
          canTransferOut: '0'
        },
        {
          fundType: '80',
          loanIn: '0',
          amount: '0',
          freeze: '0',
          overdraft: '0',
          key: 'ADA',
          canTransferOut: '0'
        },
        {
          fundType: '176',
          loanIn: '0',
          amount: '0',
          freeze: '0',
          overdraft: '0',
          key: 'ATOM',
          canTransferOut: '0'
        },
        {
          fundType: '17',
          loanIn: '0',
          amount: '0',
          freeze: '0',
          overdraft: '0',
          key: 'DASH',
          canTransferOut: '0'
        },
        {
          fundType: '211',
          loanIn: '0',
          amount: '0',
          freeze: '0',
          overdraft: '0',
          key: 'SOL',
          canTransferOut: '0'
        },
        {
          fundType: '57',
          loanIn: '0',
          amount: '0',
          freeze: '0',
          overdraft: '0',
          key: 'DOGE',
          canTransferOut: '0'
        },
        {
          fundType: '58',
          loanIn: '0',
          amount: '0',
          freeze: '0',
          overdraft: '0',
          key: 'NEO',
          canTransferOut: '0'
        }
      ],
      net: '71.223'
    }
  },
  BTC: { free: 0, used: 0, total: 0 },
  LTC: { free: 0, used: 0, total: 0 },
  TRX: { free: 0, used: 0, total: 0 },
  ETH: { free: 0, used: 0, total: 0 },
  FIL: { free: 0, used: 0, total: 0 },
  DOT: { free: 0, used: 0, total: 0 },
  ETC: { free: 0, used: 0, total: 0 },
  EOS: { free: 0, used: 0, total: 0 },
  QTUM: { free: 0, used: 0, total: 0 },
  USDT: { free: 10, used: 0, total: 10 },
  XRP: { free: 0, used: 0, total: 0 },
  QC: { free: 0, used: 0, total: 0 },
  ADA: { free: 0, used: 0, total: 0 },
  ATOM: { free: 0, used: 0, total: 0 },
  DASH: { free: 0, used: 0, total: 0 },
  SOL: { free: 0, used: 0, total: 0 },
  DOGE: { free: 0, used: 0, total: 0 },
  NEO: { free: 0, used: 0, total: 0 },
  free: {
    BTC: 0,
    LTC: 0,
    TRX: 0,
    ETH: 0,
    FIL: 0,
    DOT: 0,
    ETC: 0,
    EOS: 0,
    QTUM: 0,
    USDT: 10,
    XRP: 0,
    QC: 0,
    ADA: 0,
    ATOM: 0,
    DASH: 0,
    SOL: 0,
    DOGE: 0,
    NEO: 0
  },
  used: {
    BTC: 0,
    LTC: 0,
    TRX: 0,
    ETH: 0,
    FIL: 0,
    DOT: 0,
    ETC: 0,
    EOS: 0,
    QTUM: 0,
    USDT: 0,
    XRP: 0,
    QC: 0,
    ADA: 0,
    ATOM: 0,
    DASH: 0,
    SOL: 0,
    DOGE: 0,
    NEO: 0
  },
  total: {
    BTC: 0,
    LTC: 0,
    TRX: 0,
    ETH: 0,
    FIL: 0,
    DOT: 0,
    ETC: 0,
    EOS: 0,
    QTUM: 0,
    USDT: 10,
    XRP: 0,
    QC: 0,
    ADA: 0,
    ATOM: 0,
    DASH: 0,
    SOL: 0,
    DOGE: 0,
    NEO: 0
  }
}
```

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