Allow mass assignment of preferred_amount for GiveStoreCredit action.
Change admin config view per admin redesign in 1.3

Fix admin views_decorator.rb

Remove manage store credits text

Update promo partial and add preference_amount as attr_accessible (per the rails 3.2 security update)

Conflicts:
	app/models/spree/promotion/actions/give_store_credit.rb
	app/views/spree/admin/promotions/actions/_give_store_credit.html.erb