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.

`otherCurencies` and `consolidateOther` are WIP thing. For now, I just filtered-out unsupported ones. From here we can either go with converting them or executing in their native form (if supported by exchange).

Regarding conversion, shouldn't it rather happen in a `trade()` method?