Revert "Remove  variable from wpsc_customer_updated_data_ajax() function, as it is unused.  Not sure that it is intended to be unused, @JeffPyeBrook to review."

This reverts commit b67acd47cec25fd55b1cf2e81609171ece89fccf.
removed unreferenced variable
Merge pull request #1143 from JeffPyeBrook/pr-fix-checkout-ajax

undid unintentional changes made somewhere in the prior sequence of merges and re-organizations
Check for wpsc_gateway_container, rather than custom_gateway, when deciding which fields to not hide.  When using only a single payment gateway, custom_gateway does not exist as a class.
Consider WPSC_Data_Map experimental for now.  There is an infinite recursion error that needs to be sorted out.  Also, doc fixes and merge conflict.
Merge branch 'master' of github.com:wp-e-commerce/WP-e-Commerce