Add option to log API calls

Problem/Motivation

There currently are several bugs in the module related to invalid API requests. Many of them cannot be reproduced. Authorize.net does not keep any logs of API calls. Debugging these issues and other undiscovered issues in the module is currently impossible due to lack of ability to log API calls.

Proposed resolution

Add an option to log sanitized (card number, cvv, token) API calls to drupal's log functionality.

Remaining tasks

User interface changes

API changes

Data model changes