title: Prevent Nhibernate schemaexport from generating foreign key constraints on has many relationship
body: <p>I have a mapping like this:</p>
  
  <pre><code>HasMany(x =&gt; x.Orders).KeyColumn("CustomerID");
  </code></pre>
  
  <p>Which is causing a constraint like this to be generated by schemaexport:</p>
  
  <pre><code>alter table [CustomerOrder] 
      add constraint FK45B3FB85AF01218D 
      foreign key (CustomerID) 
      references [Customer]
  </code></pre>
  
  <p>I have tried adding .NotFound.Ignore() like on a References() mapping to disable the constraint from being generated but this does not work. </p>
  
  <p>Can a mapping be defined that will force SchemaExport to not generate the constraint?</p>