Wrong value submitted to API for business checking accounts

Problem/Motivation

When using eCheck, selecting "Business Checking" account type causes payment failure 100% of the time.

Steps to reproduce

Set up a test account, select Business Checking when submitting a payment. See in console: "E_WC_27: Please provide valid account type."

Proposed resolution

Fix the variable passed to the API for business checking. The api documentation (look for "Bank Data Properties" table and "accountType" options) shows the options as follows:

String. Either checking, savings, or businessChecking.

The code uses these options:
checking, savings, business_checking

Remaining tasks

I guess we could add a test, but this seems like a pretty trivial and obvious fix to merge, test or no.

User interface changes

none

API changes

none

Data model changes

none