Indexing the guest_token column on spree_orders

Closes #5648
Moving the default options[:lock] configuration into find_order_by_token_or_user so it can be used by both simple_current_order and current_order

Set simple_current_order to an empty order in case it's not found to avoid hitting the database needlessly

Using double quotes

Fixes #5647
Bump version
bump to beta
Fix for Promotion::Rules::Product

Using Promotion::Rules::Product rules with line item actions (Promotion::Actions::CreateItemAdjustments) was broken when the match_policy was "none".

Closes #5664

Conflicts:
	core/app/models/spree/promotion/rules/product.rb
remove line that got there by bad merge.
Improve readability in FlexiRate calculator labels
fixes #5673
Added gif to valid icon types
Fixes #5682
Merge branch '2-3-stable' of https://github.com/spree/spree into 2-3-stable