Remove append_view_path from api ControllerSetup

That line was preventing us from overriding templates within other
application or extensions

Fixes #3450
Shipments need to check if they can get rates

before trying to get them, a private method
has been added to check if the shipment is ready
to get rates, currently it only checks if the order
has set a shipping_address, if theres custom business
logic for a specific store this is what they should
be customising instead of the refresh_rates call
which is already getting too complicated by itself.

Added tests for this and had to include a before call
to stub this same call in order for the other tests to pass.

fixes #3848
fixes #3849
Simplify `can_get_rates?` in Shipment
Revert "Remove append_view_path from api ControllerSetup"

This reverts commit 92aaf03a787fc37810c07a1f8605fc4f1bb73c29.
Fixed Spree::Api::ProductsController#index to accept multiple ids

Fixes #3886
Relax money dependency