Adds passing spec for subscription order generation service
Adds new fields to begin support for pre-ordering
Subscriptions can now be created with prepaid amounts and fixed durations
Adds failing spec for prepaid subscription order
Create order macro helper
Refactors setup macros
Removes commented method
Additional test refactoring
Supports creating a prepaid subscription during finalize!
Adds failing spec for re-processing prepaid subscriptions
Skip over prepaid subscriptions until proper support exists to create automated renewals
Adds new scopes to variants
Adds prepayable_variants scope to Product
Adds #duration to variant
Adds prepayable scope to product
Adds convenience method to identify orders with prepaid variants
Merge branch 'master' into feature/generate-order-service
Generate order service should rely on the stored billing address
Merge branch 'feature/generate-order-service' into feature/subscription-preorder

Conflicts:
	app/models/spree/subscription.rb
	spec/models/spree/subscription_spec.rb
	spec/services/generate_subscription_order_spec.rb
Merge branch 'master' into feature/subscription-preorder

* master:
  Billing address is mandatory
  Adds bill and ship address methods back into the extension
  Removes bill_address association
  Removes association

Conflicts:
	app/models/spree/subscription.rb