[api] Redirect to Orders#show from Checkouts#show

Rather than having two actions that do the same thing, let's just combine all the logic into one.

API users: please use /orders/:num from this point onwards.

Conflicts:
	api/app/controllers/spree/api/base_controller.rb
Bump to 2.2.2.beta
Show tax adjustments after shipment adjustments in order details

This is because shipments can be taxed, and so it makes sense to show the tax amount immediately after showing line items 'subtotal' and the shipment
remove syntax error

remove syntax error from core engine file.

Fixes #4494
Display credit card #name [api]
Zero Order#item_count when emptying the order

Fixes #4496
Spree::Variant.deleted? returns Boolean

This change brings the `Variant` behavior in line with the `Product` behavior:

https://github.com/spree/spree/blob/master/core/app/models/spree/product.rb#L134

Fixes #4497
[api] Support order routes on /api/checkouts as well as /api/orders

I got sick of not knowing if /api/checkouts was the right prefix to use, or if I should use /api/orders. If I get sick of it after one day of usage, then I'd suspect other people who are using the API would also be sick of it.

Let's fix this problem and there will be no more getting sick of it :)
[api] Allow for accessing states inside of countries in the API

Strangely, StatesController already supported this but there wasn't a route defined for that. I only found this out today when I tried making a request to /api/countries/:country_id/states (with my spree_api_examples project) and had that fail.
[order importer] Assign created shipping rate as the selected shipping rate
[order importer] Ensure that order totals are correctly updated