Improved Credit Card Adjustments/Permissions on Squarelet

[mitchelljkotler]

This should probably wait til larger Squarelet updates, but currently to add, edit, or make other changes to the associated credit card, you have to jump through some non-intuitive hoops.

From accounts.muckrock.com, it should be easy for a user to:

• Add a new credit for use by them.
• Add a new credit card associated with an organization
• See when that credit can can be tapped and by whom (such as can it be used to pay for FOIA fees? buy more premium credits?)
• Potentially modify the scope
• Optionally carry a credit balance from refunds, etc?

It might be useful to let some configuration of how payment permissions can work, such as allowing a card to be charged for FOIA fees by anyone in an organization, though that would add complexity