fix binding readonly properties

[ElizabethOkerio]

This PR fixes #1026

In this fix #993 we added a fix to remove duplicate joins from the generated sql. This involved making updates to the Instance property of the expression to be created and only including structural properties.

The changes led to this being generated:

{ Instance = new Customer() {Id = $it.Id, Name= $it.Name}}

Instead of this:

{ Instance = $it }

    foreach (PropertyInfo prop in props)
            {
                foreach (var sp in structuralProperties)
                {
                    if (sp.Name == prop.Name)
                    {
                        MemberExpression propertyExpression = Expression.Property(source, prop);
                        bindings.Add(Expression.Bind(prop, propertyExpression));
                        break;
                    }
                }
            }

This is the code that recreates the Instance to only have structural properties.. Calling Bind on a read-only property that doesn't have a setter will throw exceptions. This fix adds a check to check if a property has a setter. If it has a setter then we can do a bind, otherwise we don't.

The readonly properties will be on the response. This won't affect.

[gathogojr]

@ElizabethOkerio When we had, { Instance = $it }, what was preventing the readonly properties from causing chaos given that $it implies everything (I think)?

[habbes]

Would be great to explain in the PR description why read-only properties are included in the response even when they are not explicitly added to the instance.