added is_active property to BillingAccount along with migration
added active accounts to billing info handler
added billing account active status to account list
added ability to deactivate / activate accounts via the account form. upon deactivation, option to choose transfer account for subscriptions associated with the current account
better success messages on filling out the account form
Merge pull request #3645 from dimagi/deactivate-billing-acct

Ability to Deactivate Billing Account