Support read-only properties somehow

[Zruty0]

As mentioned in #254 , now that we are supporting both fields and properties for the purposes of schema comprehension, it is possible to create properties that act like 'calculated fields':

        public class MyDataRow
        {
            private DateTime _dateTime;

            public float Day { get { return _dateTime.Day; } }
            public float DayOfWeek { get { return (float)_dateTime.DayOfWeek; } }
            // etc
        }

But the above code is not sufficient, because currently we require both getter and setter to be present (and public). So you have to add the fake setters that throw.

Is there a way to have it both ways somehow? We want to ensure that we'll be able to write to a property (in case when we use the underlying class as output), but we also want to allow read-only properties (in case when we use it as input).

@TomFinley , do you have a recommendation? I am leaning towards allowing getter-only (or private-setter) properties to live, but only for input classes. This means that SchemaDefinition / InternalSchemaDefinition should have some IsReadOnly tracking, and corresponding error/warning messages in case we attempt to generate a 'poke' method for a read-only property .

[TomFinley]

Hi @Zruty0 seems like what you've suggested is good. Tracking and error if these read only properties (and fields!) acceptable for input with a copy to support the ref call seems good to me. We will want something like this for F# support for sure.

[Zruty0]

@TomFinley please take a look at #640 , I think this is good enough to be merged.