Ability to add projection on entity.

This functionality is needed in order to support many scenarios in NHibernate.Linq. This feature is directly related with Subquery Projection.

One example use can be:

rootCriteria.SetProjection(Projections.ProjectionList()
.Add(Projections.Entity("c"))
.Add(Projections.Alias(Projections.SubQuery(visitor.Criteria), "orderby"));

One concrete example of where this is necessary is the following linq query:

from c in customer
orderby c.Orders.Count
select c;

which should roughly translate to the following SQL query:

select
c.*,
(select count from Orders e where e.CustomerID = c.CustomerID) orderby
from Customers c
order by orderby

Priority set to major in order to support nhibernate features