NH-3807 - Clean up some namespaces.

Use System.Collections.ObjectModel.ObservableCollection instead of the now removed Remotion version.

Author: ngbrown

src/NHibernate/Linq/Clauses/NhJoinClause.cs

@@ -1,10 +1,10 @@
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Linq.Expressions;
 using NHibernate.Linq.Visitors;
 using Remotion.Linq.Clauses;
 using Remotion.Linq.Clauses.Expressions;
-using Remotion.Linq.Collections;
 
 namespace NHibernate.Linq.Clauses
 {
@@ -59,4 +59,4 @@ public override void TransformExpressions(Func<Expression, Expression> transform
 			base.TransformExpressions(transformation);
 		}
 	}
-}
+}

src/NHibernate/Transaction/ITransactionFactory.cs

@@ -1,7 +1,4 @@
 using System.Collections;
-using System.Transactions;
-using NHibernate;
-using NHibernate.AdoNet;
 using NHibernate.Engine;
 using NHibernate.Engine.Transaction;
 
@@ -34,4 +31,4 @@ public interface ITransactionFactory
 
 		void ExecuteWorkInIsolation(ISessionImplementor session, IIsolatedWork work, bool transacted);
 	}
-}
+}