create interceptor-system for Ejecta


This pull request is about #384

I don't use Event-pattern , instead ,   I choose interceptor.

The interceptor  could  process the data of  js file /image file/audio file , before they are be used in Ejecta.

If user  doesn't  create or enable  any interceptor ,  nothing will happen.

=============================

Extension/EJBindingDecryptorXOR.m  is just a default   Decryptor-interceptor. 
It shows how to create and use an interceptor.

There is an example App  :  <http://fattyboy.cn/App.zip>

in this  App.zip  , there is an  Encryptor.js , it is used for encrypting files ,
then  when App is running ,  EJBindingDecryptorXOR will decryptor   encrypted files.