INT-1871 TCP CachingClientConnectionFactory

Pool based on algorithm used for spring-integration-file
CachingSessionFactory introduced by INT-2146. Refactored
that code to use the common SimplePool.

One difference to the previous implementation is the
ability to change the pool size dynamically.

If the size is reduced and more than the new size are
in use, items are closed as they are returned until
the pool size is as requested.

Initial commit.

Allow Pool Size Changes

Factor out Pool

Polishing

Pool Tests

Default forever

Javadocs, File

Polishing

INT-1871 PR Polishing

* Consistent/cleaner method names
* Track checkouts; reject release of 'foreign' objects.
* Add 'getAllocatedCount()'

spring-integration-ftp/src/test/java/org/springframework/integration/ftp/session/SessionFactoryTests.java

@@ -27,6 +27,7 @@ import org.apache.commons.net.ftp.FTPClient;
 import org.junit.Ignore;
 import org.junit.Test;
 import org.mockito.Mockito;
+import org.springframework.integration.MessagingException;
 import org.springframework.integration.file.remote.session.CachingSessionFactory;
 import org.springframework.integration.file.remote.session.Session;
 import org.springframework.integration.file.remote.session.SessionFactory;
@@ -133,7 +134,7 @@ public class SessionFactoryTests {
 		Mockito.verify(sessionFactory, Mockito.times(2)).getSession();
 	}
 	
-	@Test (expected=IllegalStateException.class) // timeout expire
+	@Test (expected=MessagingException.class) // timeout expire
 	public void testSessionWaitExpire() throws Exception{
 		SessionFactory sessionFactory = Mockito.mock(SessionFactory.class);
 		Session session = Mockito.mock(Session.class);