title: Ignore column using mapping by code in HNibernate
body: <p>I'm using mapping by code in NHibernate.
  I got a class with several properties. One of them is not related to any columns in DB but still has getter and setter.</p>
  
  <p>I use ConventionModelMapper not ModelMapper. The first one assumes that all properties are mapped.</p>
  
  <p>How i can tell to NHibernate to ignore it?</p>