Stop individually deleting objects at the end of each ObjectTortureTest.

We can now do this since the entire scene and all objects within it are now successfully gc'd at the end of these tests.
This greatly improves the time taken to run each test (by reducing teardown time, not the time to actually do the test work that we're interested in).
Slightly simplifies config read in Scene constructor to help facilitate this.

OpenSim/Tests/Torture/ScriptTortureTests.cs

@@ -91,6 +91,14 @@ namespace OpenSim.Tests.Torture
             m_scene.StartScripts();
         }
 
+        [TearDown]
+        public void TearDown()
+        {
+            m_scene.Close();
+            GC.Collect();
+            GC.WaitForPendingFinalizers();
+        }
+
         [Test]
         public void TestCompileAndStart100Scripts()
         {