Add a HOLD state to Phortune and handle unusual states better

Summary:
Ref T2787. When Paypal comes back to us with funds on hold, dead-end the transaction but handle it properly.

Generally, smooth out the user interaction on weird states.

Implement refudnds/cancels for Paypal.

Test Plan:

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T2787

Differential Revision: https://secure.phabricator.com/D10667