Clean up JNIHelper
Use an obtained class loader instead of the default
Remove JNI_OnLoad() since we've moved to using the NDK activity APIs
Separate calls to setvm reference and to set classloader
Cache JNIEnv
Use default class loader to obtain the ClassLoader for this NativeActivity
Actually obtain a reference to the Java class
Initialize Cocos2dxHelper from JNI. Call System.loadLibrary() in Java so functions implemented in native code are available from Java.