Localization for request submit flag and reason

[ctgraham]

Is your feature request related to a problem? Please describe.

Pending RockefellerArchiveCenter#234, we need a way to permit all requests to be submitted within DIMES, regardless of RAC's business logic. We also modify the "error" messages returned for items with potential submission "problems".

Describe the solution you'd like

We've edited Processor.is_submittable.

Describe alternatives you've considered

n/a

Additional context

This local is expected to be transient.