Add logging when more than 1 CodePush instance is created

Author: geof90

android/app/src/main/java/com/microsoft/codepush/react/CodePush.java

@@ -101,6 +101,10 @@ public CodePush(String deploymentKey, Activity mainActivity, boolean isDebugMode
         }
 
         initializeUpdateAfterRestart();
+        if (currentInstance != null) {
+            CodePushUtils.log("More than one CodePush instances has been initialized, please use the non-static method codePush.getBundleUrlInternal() to get the correct bundleURL for a particular instance.");
+        }
+
         currentInstance = this;
     }