fix(trader): Ensure consolidation of only same-currency trades

Changes include:
* unbinding _private_, and pure methods from prototype of a `Trader` object:
  * `Trader.prototype._findExchange` => `findExchange`,
  * `Trader.prototype._findTicker` => `findTicker`,
  * `Trader.prototype._findTrader` => `findTrader`,
  * `Trader.prototype._findWallet` => `findWallet`.

* Some local variables renamed to improve readability:
  * `tradeRec` => `consolidatedTrade`
  * `tickerExchangeCode` => `tickerName`,
  * `tickerExchangeConfig` => `tickerConfig`,
  * `tradeExchangeCode` => `traderName`,
  * `tradeExchangeCode` => `traderConfig`,
  * `transferExchangeCode` => `walletName`,
  * `transferExchangeConfig` => `walletConfig`.

* Since addition is commutative and order of looping doesn't matter: `while (true)` loop changed to `for..in`,
* `consolidateOther` and `otherCurencies` are used to consolidate if other currencies occur in queue.

This solution doesn't make sense to me. From what I can see, otherCurrencies never gets used anywhere. If we just convert all trades to the target exchange currency during ```_consolidateTrades```, it will simplify the code a lot, and it will correctly incorporate those trades. I don't see a downside to this, is there something I'm missing?