Extract amazon payment account into its own model
Break down new project workflow into two steps

First you create a project, then you connect an Amazon account to it.
This makes testing much easier, and lets the user preview their project
to give them extra incentive to finish.
Restore Amazon functionality with a temporary hack
Add AmazonPaymentController scaffolding
Failing specs for amazon payment account controller
Start molding the AmazonPaymentAccountController

Remove unneeded actions, start setting up new, create, and destroy
Refactor amazon lib a bit
Passing tests!
Start moving projects#save to payment_accounts#create
Fix a bunch of tests to comply with earlier changes

This commit includes a lot of refactoring of the amazon libraries
so that they're easier to understand. It also gets all of the tests
passing again.
Add authorization to the payment account actions