Minor cleanups to USB MIDI handling

In testing, the releaseInterface() call was found to be unreliable, so
this patch omits the call. Also minor copyright header fix.

android/src/com/levien/synthesizer/android/ui/PianoActivity2.java

@@ -227,11 +227,13 @@ public class PianoActivity2 extends Activity {
         usbMidiDevice_ = null;
       }
       if (usbMidiInterface_ != null) {
-        usbMidiConnection_.releaseInterface(usbMidiInterface_);
+        // Note: releasing the interface seems to trigger bugs, so
+        // based on experimentation just closing seems more robust
+        //usbMidiConnection_.releaseInterface(usbMidiInterface_);
       }
       usbMidiConnection_.close();
-      usbMidiDeviceName_ = null;
       usbMidiConnection_ = null;
+      usbMidiDeviceName_ = null;
     }
     if (device != null && intf != null) {
       UsbManager usbManager = (UsbManager) getSystemService(Context.USB_SERVICE);

android/src/com/levien/synthesizer/android/usb/UsbMidiDevice.java

@@ -1,4 +1,18 @@
-// TODO copyright
+/*
+ * Copyright 2013 Google Inc.
+ * 
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ * 
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ * 
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
 
 // Class representing a USB MIDI keyboard