* Fix - Escape line item value
* Fix - Added maxlength to MD5 Hash field as Authorize.net truncates the md5 to 20 characters.
* Tweak - New wrapper class with common helper methods (log and get_settings) in plugin's main file.
* Tweak - Validate API credentials in settings page.
* Tweak - Support refund via Authorize.Net.
* Tweak - Capture the Authorize.Net transaction when order status is changed to in-processing or completed.
* Tweak - Void the Authorize.Net transaction when order is cancelled (only for unsettled transaction with order status on-hold) or refunded.
* Fix - Auth-only mode should set order status to on-hold.
