7.x 4.x litle sustainers

Adds the ability to accept recurring payments through the Litle payment gateway when using a credit card.  This should be ready for review and further testing.  This doesn't include the echeck / bank account recurring payments.

Steps for testing:
1.  On the payment method configuration page (where you enter credentials and other settings) enable sandbox mode and enable card on file.
2.  Set up a donation form with Litle credit card payment and recurring enabled.
3.  Submit with test data from the Litle API doc.  This will cause an auth request and sale request with the card data, then a register token request.  The token will be stored as the remote_id in cardonfile.
4.  When the recurring payments are processed, an auth request and sale request are made with the token instead of the card data.

Because of the way the sandbox works, when in sandbox mode the data is hardcoded for some of the requests in order to force a successful transaction.  I haven't figured out a good way to test the same data end to end.