multipage checkout

This is considerably easier to make changes to than the former single
page checkout. Steps are also seamlessly skipped if not needed such as
shipping/payment.
added view and partial functions to MY_Controller.php
update language file for multi-page checkout
updated GoCart additional detail code.
increased CVV code to 4 characters
no longer needed.
Check to see if the field exists in migrations before removing it.
fixed problem with base rates
Fix shipping loop if no shipping options exist
Correct spelling (thx briangelhaus)
update change log
updated
updated
updated
removed duplicate form_login (thx dronord)
translatable 'Login', 'Register', 'Checkout' on page view_cart
translatable 'Search' in header
translatable 'Catalog' in header
translatable 'Inventory' on page product_form
translatable 'Home', 'Actions' in admin header