Added Shipping and Taxes Copy

Added the ability to copy existing tax rates and shipping methods.  The copy allows you to create shipping rates and taxes that are similar to existing rates.

To create a copy:

  1. Click on the edit link for the tax rate or shipping method you wish to copy
  2. Click on the copy link, located at the top right
  3. The existing rate will be copied, with the word copy added to the end
  4. Make any necessary changes to the new shipping method/tax
  5. Hit Save

Note that this feature applies to the new shipping methods.