Add initializer tests and move classpath files

The initializer tests verify that every non-optional initializer, this
includes Providers, is loadable.

Creating files under META-INF is not considered best practice. Smack's
configuration and provider files reside now in classpath directory
qualified by Smack's package namespace.

core/src/test/java/org/jivesoftware/smack/SmackConfigurationTest.java

@@ -0,0 +1,17 @@
+package org.jivesoftware.smack;
+
+import static org.junit.Assert.fail;
+
+import org.junit.Test;
+
+public class SmackConfigurationTest {
+
+    @Test
+    public void testSmackConfiguration() {
+        try {
+            SmackConfiguration.getPacketReplyTimeout();
+        } catch (Throwable t) {
+            fail("SmackConfiguration threw Throwable");
+        }
+    }
+}

core/src/test/java/org/jivesoftware/smack/initializer/CoreInitializerTest.java

@@ -0,0 +1,17 @@
+package org.jivesoftware.smack.initializer;
+
+import static org.junit.Assert.assertTrue;
+
+import org.jivesoftware.smack.initializer.CoreInitializer;
+import org.junit.Test;
+
+public class CoreInitializerTest {
+
+    @Test
+    public void testCoreInitializer() {
+        CoreInitializer ci = new CoreInitializer();
+        ci.initialize();
+        assertTrue(ci.getExceptions().size() == 0);
+    }
+
+}