uc_authnet 6.x-2.0-beta1

The 2.x branch is a complete rewrite. Originally, it was a submodule of the Authorize.net API project (http://drupal.org/project/authnet), but we decided to break it out into it's own, and the previous maintainer of uc_authnet agreed to combine efforts.

For more info, see: #1905594: Move Ubercart integration to uc_authnet contrib project