title: Trying to modify the type of a field with .WithDefaultValue()
body: <p>I have a table with a column that has a default value:</p>
  
  <pre><code>this.Create.Table("msgqueue")
      .WithColumn("id")
          .AsInt32()
          .Identity()
          .PrimaryKey()
      .WithColumn("queueddt")
          .AsDateTime()
          .Nullable()
          .WithDefaultValue(SystemMethods.CurrentDateTime)
  ;
  </code></pre>
  
  <p>I want to change this from datetime to datetime2:</p>
  
  <pre><code>this.Alter.Table("msgqueue")
      .AlterColumn("queueddt")
          .AsCustom("datetime2")
          .Nullable()
          .WithDefaultValue(SystemMethods.CurrentDateTime)
  ;
  </code></pre>
  
  <p>This gives me errors:</p>
  
  <pre><code>The error was The object 'DF_msgqueue_queueddt' is dependent on column 'queueddt'.
  </code></pre>
  
  <p>I did some googling around, and discovered Delete.DefaultConstraint(), so I tried that, first:</p>
  
  <pre><code>this.Delete.DefaultConstraint()
      .OnTable("msgqueue")
      .OnColumn("msgqueue")
  ;
  </code></pre>
  
  <p>And I still see the same problem.</p>