Adds the ability for negative postcode matching conditions in the Shipping modules. Syntax for negative conditions is a ! at the very begining of the whole matching set.
Refactored exclusive postcode handling and added support for individual rule exclusions by adding '!' to the beginning of the rule.
Replaced anonymous function with create_function for PHP 5.2 support and cleaned up variable names.
Merge pull request #2417 from msigley/patch20130912

Negative postcode matching in shipping modules