Add "app.content.type" and "app.paging.size" to app.conf.

* app.content.type : dynamically change type of content area.
* app.paging.size : dynamically change the size of paging data.
* module.init: add variable "_t" for total row in paging.
* module.main.layout.css: add icon for "add", "edit", "refresh", and "delete".
* module.main.layout.js: dynamic content area, based on "app.content.type".
SystemUser: change to object oriented.