Enforced waits for auditors and authorizations

Two major fixes for making GDrive permissions wait for certain data:
* Audit.prototype.findAuditors() now returns a Deferred that resolves to the auditors only when all have been loaded and are ready.
* Loading authorizations for a Program in gdrive_workflows_controller now uses refresh_instances on the binding, instead of calling .get_mapping("authorizations")

There is an optional flag added to findAuditors() to operate in the classical style, because if_auditor would need to defer_render, and if_helpers currently can't work with helpers that defer (we have if_auditor in if_helpers in several places).