Allow inventory tracking control (enable/disable) at the variant level. This retains the site-wide inventory tracking flag, but also allows this type of control down at the variant level.

Fixes #3974

Conflicts:
	core/app/models/spree/stock_item.rb
	core/app/models/spree/variant.rb
	core/spec/models/spree/variant_spec.rb
Use different id on hidden field so associated labels work as expected

Fixes #3981
position should not be present in taxon_attributes
Taxon sorting for 2-1-stable fix

Fixes #3989
use a better name for the method that restarts the checkout flow,also make sure we use the checkout_steps.first instead of hardcoding it to "address".

use expect syntax

use the correct syntax
(backend) in order details, line items states could not be translated

Fixes #4009
[backend] verifying if product picker returns any product

Fixes #4008
do not call move_to_child_with_index when the taxon is new, since this
is not supported by acts_as_nested_set.

Fixes #3999
Show log entries in the admin backend

Working towards a solution for #3978
[backend] Fix issue where database cleaner was not truncating tables
Bump kaminari to 0.15.0
Go with whatever money gem activemerchant depends on
Touch shipment when IUs are updated, and touch order if Payments or Shipments change
Remove extra line from ResourceController#model_class that was added in #3974

This line causes this issue: https://github.com/spree/spree/pull/3974#issuecomment-29130309
Stub touch on mocked Order in shipment_spec
Don't override accessor if model has column already

Say users want to add a `name` column in spree_variants. They can't make
use of that attr on a variant instance because Spree would always
delegate that method to a product.

Now it would only delegate if the model doesn't have that column. That
would be all cases in a default scenario.

Fixes #4012
Move ::Money.extract_cents and ::Money.parse to Spree::Money, as those methods are being deprecated and we care about them.

Conflicts:
	core/lib/spree/money.rb
Add missing link for log entries
[backend] Use display_amount to display payment amount in payments/show
Include UTF-8 encoding in money.rb