Getting ready for Teatro.io stage server
Merge pull request #5067 from semenyukdmitriy/teatro_stage

Getting ready for Teatro.io stage server
Validate uniqueness of order numbers... Why was this FIXME never fixed until now... Fixes #5102
Add `Spree::Promotion#products` back.

Currently used in the frontend.

Closes #5071
Add mail_from_address field to general settings page

Closes #5047
Allow the admin to specify a preferred refund type

Changes give an admin the opportunity to specify a preferred way to
refund a customer (when multiple methods are available) when creating an
RMA and when creating a return authorization.

Also fixes the x icon on select2 selectboxes.