Must specify class_name for order association on LineItem

So that it doesn't attempt to look up Order and not Spree::Order when assigning it via association
Fix translation issue for no and yes keys in YAML

Fixes #2763
Change in amount precision limit

Fixes #2715
Fixes #2716
Change in amount precision for spree adjustments

Fixes #2715
Fixes #2716
Update extension generator dependency versions.

Fixes #2743
Empty user promotion rule should not be eligible

Fixes #2749
Run extension installation generator during rake test_app.

Fixes #2741
Minor refactor: extract gateway order id to method

This will allow people to more easily override the order id passed
in to the payment gateway.  It will behave the same for existing
functionality.

Fixes #2732

Conflicts:
	core/app/models/spree/payment/processing.rb
Correct filename for diners club credit card icon

Fixes #2726

Conflicts:
	frontend/app/assets/images/credit_cards/icons/diners_club.png
Fix styles for empty orders list in admin

Fixes #2734
Fix email validation error I18n symbol lookup

And include %{value} for interpolation in validation messages.

The current code hardcodes the I18n key and improperly assigns the error
which leads to several problems:
* You cannot override the translation message for models/attributes
* You cannot pass your own I18n key as a symbol (eg. :invalid_email)
* You cannot use symbol interpolation

This fixes the above problems and is the proper solution for issue #2346.

This fix also applies to 1-2-stable and 1-3-stable.
For a fix against 1-1-stable see PR #2729.

Fixes #2730
Modify the look of the coupon code.

This moves coupon code to be better aligned with the cart buttons.
This significantly improves the way things look in alternate
localizations.

Fixes #2720
Correct content length check in base_helper_spec test for meta_data_tags
admin tabs are displayed only if user has :admin right on resource

Fixes #2626
Specify :class_name options for InventoryUnit associations so that assigning them doesn't fail

This is due to an AR bug which assumes the class is not namespaced.
Specify :class_name for has_many images on Variant

Previously, attempting to assign invalid data (i.e. variant.images = [nil]) to this association would've resulted in an uninitialized constant error for Image, rather than erroring correctly on an association class mismatch.
Changed line items to display cost-per-unit using the single_money method instead of display_amount from the associated variant

Fixes #2772
nested_taxons_path will now take a Taxon object and generate a proper URL
add a check to prevent skipping checkout steps

Fixes #2764
feature : taxons meta tags and title

Fixes #2787