Info for products with multiple variants

Setting SKUs for products with multiple variants can be confusing for novice users.

This adds a note on the product form in the place where the SKU field would normally appear. It lists several variant SKUs and invites the user to manage product variants.

Fixes #4897
Bump to Rails 4.1.4
Added without_children = true in taxon autocomplete API Call

We do not need taxon children in autocomplete of product taxons. As we were loading taxon children the response of the API call was slow.

Fixes #4903
Optimize available_countries

Use .sort_by so that we only run .parameterize once per country.

Fixes #4899
Destroy associated adjustments when order is changed to move out of taxable zones.

Fixes #4840
Fixes #4839
Fixes #4916
refactored and fixed tax rate spec

Fixes #4839
Fixes #4840
Fixes #4916
NO TOUCHING in OptionValue#touch_all_variants
optimize touch_all_products performance

use sql update instead of touch each products.

Fixes #4910
Permit first_name and last_name in address attributes

These parameters are aliases for firstname and lastname, and so should be permitted through as well.

This used to work in 2-2-stable, but was broken as of 2-3-stable.