Add OCM support

[perandersson]

Add support for OCM classes:

First create an object content manager with at least these methods:

public interface IObjectContentManager
{
   void insert(object entity);

   void remove(object entity);
}

Secondly - create attributes used on the class to specify which fields to expose to the content repository tree:

[Node]
public class MyObject
{
   [NodeValue]
   public string Value1 { get; set; }

   [NodeValue]
   [NodePath]
   public string Path { get; set; }
}