Move zk.wpd to static assets folder

User Story

As a user, I want Http server to serve all static assets, such as Image, JS, and CSS, so that it's better to get rid of zk.wpd for JS files by using pure JS file instead.

Acceptance Criteria

All assets can be put outside Application server (i.e. Tomcat or Jetty), the user can specify it into a Nginx or Apache server to serve, if not specified, the assets can also be served by ZK server inside a jar or similar mechanism.