Implement Profile Metadata Abstraction

[boatmeme]

Still too early in reverse engineering the RT4 format to know how valuable this might be, but I can imagine a use case for settings / values that represent read-only properties like created_date, firmware_revision, and header , and that these aren't necessarily best represented as RetroTinkSetting objects.

One approach could be to add a read-only property to RetroTinkSetting.

Another would be to maintain a separate metadata: RetroTinkSettings property of RetroTinkProfile that contains the definitions for all of the read-only values in the RT4.

Whatever path we choose, we must consider how we can best prevent / discourage developers from attempting to update those values.