Initial external shipping implementation
Adding tests for external shipping
Fixing @cover annotations
adding is_changed logic to shipping models
Fixing Shipping_Item_External, adding methods in Shipping and Shipping_External to allow for overriding the public API
Extending the models for external shipping support
refactoring shipping items location update logic to support addresses and be inside the items themselves
Adding tests for new methods and refactoring where needed
Converting Shipping_External to abstract, adding Dummy implementation for tests
Changing Model_Shipping::groups_in from public to protected, fixing tests
Fixing array comparison in Model_Shipping::is_changed
Removing paranoid logic from Model_Shipping_Item_External::shipping_external_data_insist
Fixing formatting, adding copyright info, removing some unnecessary docs
Merge pull request #3 from OpenBuildings/external-shipping

External shipping