New Payment dialog structure
Summary:
This implements the new payment dialog structure as requested in https://bifrost.kolabsystems.com/T380342.
No new payment methods are enabled yet, so impact should be minimal.
Test Plan: phpunit tests
Reviewers: #hkccp_developers, machniak
Reviewed By: machniak
Subscribers: bohlender
Differential Revision: https://git.kolab.org/D2239