Authorize SIM Method

Talking with one of the developers for EC, and I noted that I had a need for the SIM version of Authorize.net, where you don't need a SSL. Attached is the majority of my code, where someone could implement the SIM system with very little effort. This is actually a separate module, but could be combined into the current module. The only key part of this setup that's missing is the response for the user when the transaction is complete, where the programmer could do a drupal_goto or print out a message (near the bottom of the .module file). Regardless, hopefully this will help a developer get most of the work done if they need it, or help the developers to push out a committed version.