Add readonly optional fields to fill Device information from UISP API

[WillNilges]

We can add a property decorator on a function on the Device Model object that will let us back certain Device fields with the UISP API. Implementing it this way would mean that doing things like branching in the UI/Admin Panel code based on having this info would be trivial.

Relates to: #404

[Andrew-Dickinson]

We should probably cache the UISP API response JSON in memory on the model object, and only fetch it if needed the first time, rather than making an HTTP call for every field separately

[WillNilges]

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