Feat/onsite payments

Adding support for onsite payments include: Scholarships, Account Transfers, Cash and Check
 - Ability to refund all types of payments is now supported
 - Adding multiple payments per modal session is supported
 - Refactored modal controllers and files so that errorModal.js isn't used for things other than errors.  Also Payments had enough logic that paymentModal.js was easily justified

This update is dependent upon https://github.com/CruGlobal/conf-registration-api/pull/152 to be reviewed and deployed first.