R1:89a6ed98e7b8

Use real icons for payment providers

Summary: Ref T2787. Uses the real icons. Straightens out the add payment flow a tiny bit.

Test Plan: {F214922}

Reviewers: btrahan, chad

Reviewed By: chad

Subscribers: epriestley

Maniphest Tasks: T2787

Differential Revision: https://secure.phabricator.com/D10654