Shipping re-integration

Everyone who follows the changes of the CVS repository of mambo-phpShop may have seen the changes and the recent Changlog. I've begun to rebuild the way, Shipping is handled in mambo-phpShop. I moved all Shipping Module Code (which previously was shattered among several files) into separate classes for each Shipping Module. Now each Shipping Module provides a class with an API for

• Calculation of Shipping costs,
• Listing available Shipping Rates and
  
• Validating a selected Shipping Method.

I removed the old Intershipper module, files & Table and added new Intershipper Code which is able to interact with InterShipper.com using a XML Syntax to fetch the Rates online.
Intershipper stays highly configurable! UPS code will be added too. The changes made it necessary to also change Configuration Parameters & Parameter names in the phpshop.cfg.php!! Each Shipping Module now has its own configuration file under /classes/shipping (when necessary). The currently active Shipping Module for your Shop (there can be only one) is the value of the new global Parameter "PSHOP_SHIPPING_MODULE". It can have the values "standard_shipping", "zone_shipping", "intershipper", "no_shipping" and "ups".