Fixing ExceptionRenderer so it can render exceptions that are subclasses

of CakeException that do not have custom templates, like ConfigureException.
Removing $lastError as it doesn't work.
Added tests.

lib/Cake/tests/Case/Error/ExceptionRendererTest.php

@@ -574,6 +574,16 @@ class ExceptionRendererTest extends CakeTestCase {
 					'/Internal Error/'
 				),
 				500
+			),
+			array(
+				new CakeException('base class'),
+				array('/Internal Error/'),
+				500
+			),
+			array(
+				new ConfigureException('No file'),
+				array('/Internal Error/'),
+				500
 			)
 		);
 	}