[GNC] Default to Plain English instead of Debit and Credit

[flywire]

Is it CR or DB? Who knows, toss a coin:
https://bugs.gnucash.org/show_bug.cgi?id=798964

An interesting list of accounts adapted from a comment with an `*` next to
the main account types:

* BALANCE ACCCOUNT TYPE       DEBIT    CREDIT
  debit            NONE       Funds In Funds Out
  debit            BANK       Deposit  Withdrawal
  debit            CASH       Receive  Spend
  debit            CREDIT     Payment  Charge
* Debit            ASSET      Increase Decrease
* Credit           LIABILITY  Decrease Increase
  debit            STOCK      Buy      Sell
  debit            MUTUAL     Buy      Sell
  debit            CURRENCY   Buy      Sell
* Credit           INCOME     Charge   Income
* Debit            EXPENSE    Expense  Rebate
* Credit           PAYABLE    Payment  Bill
* Debit            RECEIVABLE Invoice  Payment
  credit           TRADING    Decrease Increase
* Credit           EQUITY     Decrease Increase

Regards