clean up package remaming and change default background from brown to gray
check in

   * 2013-03-09

      * add grouping
      * show grouping in homepage
      * copy meilishuo's css style in grouping

   * 2013-03-12

      * add Product trait to model all products
      * add Dress (not finished yet)

   * 2013-03-13

      * add apache server to serve images
      * add utilities to download/upload images from/to this server
      * add project configurations, e.g. image server address
      * almost finish Dress modeling, except for Retailer and Brand
      * remove some deprecated warnings

   * 2013-03-14

      * add utility function to get a binary file from an http server
      * bring up admin page
      * rename Dress to Product because it contains general info about
any product
refactor modeling

use Mapper to implement relations among main entities, like Retailer,
Supplier,Product,Storage,Shop etc.
reorganize source files
refactor homepage grouping by using Product

* improve db schema
* cleanup code
fix top product;
add sales count to product and storage
use http server to host images
dynamically load images from product and storage objs