Replace isOpen with status

[mkimberlin]

As an Administrator, I want the isOpen field for review periods to be converted to an enumeration field named status with potential values Planning, Awaiting Approval, Open, and Closed so that I can easily understand and manage the workflow of each review period.

Acceptance Criteria

• The isOpen field on the ReviewPeriod model is removed.
• A new field named status of type enumeration is added to the ReviewPeriod model with the following allowed values: Planning, Awaiting Approval, Open, and Closed.
• Existing data is migrated such that true in the isOpen field becomes Open in the new status field and false becomes Closed.

[mjperry91]

#2273

[S78901]

@mjperry91 Please let me know once this is merged so I can finalize Issue #2220.