Move admin files out of frontend and into backend
Added BSD-3 license with copyright.

Copyright to Spree Commerce Inc. and other contributors.

Fixes #2274
[api] Allow a Rabl template to be specified during a request

Conflicts:

	api/app/controllers/spree/api/base_controller.rb
	api/app/controllers/spree/api/taxons_controller.rb
Allow option values to be deleted from the admin backend

Fixes #2277
[api] Add option values endpoint
[api] Fix require to common_rake within Rakefile
Remove jasmine dependency
Move Spree::Admin::OptionValuesController to backend
[core] Remove calculated_adjustments call from ShippingMethod

This is now automatically done when the CalculatedAdjustment module is
included into ShippingMethod
[api] Move InventoryUnitsController to correct location
Move capybara_ext and price_factory into correct testing_support directory
Move ResourceController spec from core into backend
Move current_order_ip_tracking_spec into frontend
Add HBD for CalculatedAdjustments#compute_amount method
Move currency_spec into frontend
Mark order_updater tests for update_adjustments as pending for now
Turning backend into a gem; separating and re-arranging more things in
frontend

Add requires for backend and frontend to spree.rb
Remove Spree::Core::StoreHelpers, replaced with Spree::StoreHelper

Remove store_helpers
[dash] sync platform_type to Jirafe
Remove commented out factory from payment_factory