Remove the explicit mapping model build step

[jagregory]

Mapping parts have a method that looks something like this:

public ClassMapping GetClassMapping()
{
    mapping.Name = typeof(T).AssemblyQualifiedName;

    foreach (var property in properties)
        mapping.AddProperty(property.GetPropertyMapping());

    ....
}

Ideally, the underlying mapping model would always be "up to date" rather than requiring this explicit build step.