Remove 'disabled' from inputs in payments

With the Aug 27 commit, a601035bd199a49f7f74ccf04ed0d889ca895f3e, the inputs under `.payment-method` are being disabled on line 15 but never correctly undisabled. This fixes that issue. Looks like it is affecting most branches.
fixes #5467
Ignore guides.
Make best-promotion query more deterministic

Mostly for the benefit of the specs under MySQL.

This query was generating some sporadic spec failures for me when using MySQL as the database. This is because MySQL does not store fractional seconds so the "created_at" was sometimes the same value for two adjustments when running specs. And when created_at is identical the query below would actually pick the earlier adjustment instead of the more recent one.  Adding "id" as a fallback ordering fixes this problem and makes the behavior more deterministic.

The issue is reproduceable in postgres as well by using Timecop.

Fixes #4943
Fix running just rake for specs.

Conflicts:
	core/spec/lib/spree/core/controller_helpers/auth_spec.rb
Fix rerunning sample specs without new dummy app.
Check payment method should respond to cancel. Fixes #5307
Improve the presentation during creating prototypes. Fixes #2526
Use slower but robust ActiveRecord for migration

When I ran this migration on my 2-1-stable store, I got the following exception:

    StandardError: An error has occurred, all later migrations canceled:

    Mysql2::Error: Column 'shipment_total' cannot be null: UPDATE spree_orders
                 SET shipment_total = (SELECT SUM(spree_shipments.cost) AS sum_id
                                       FROM spree_shipments
                                       WHERE spree_shipments.order_id = spree_orders.id)
                 WHERE spree_orders.completed_at IS NOT NULL AND spree_orders.shipment_total = 0/Users/username/appname/db/migrate/20140609012476_set_shipment_total_for_users_upgrading.spree.rb:7:in `up'
    ActiveRecord::StatementInvalid: Mysql2::Error: Column 'shipment_total' cannot be null: UPDATE spree_orders
                 SET shipment_total = (SELECT SUM(spree_shipments.cost) AS sum_id
                                       FROM spree_shipments
                                       WHERE spree_shipments.order_id = spree_orders.id)
                 WHERE spree_orders.completed_at IS NOT NULL AND spree_orders.shipment_total = 0

Rephrasing the raw SQL into ActiveRecord, the migration ran slower but didn’t crash.

(I was intending to add `if shipments && shipments.sum(:cost)` to line 7 but surprisingly didn’t need to.)

Fixes #4823
No need for partial. Fixes #5475
Looking up stock location by the admin name as well

fixes #5484
Add spec for looking up stock location by admin name.
Do not allow leading or trailing dot(.) in the first part of email address

Add rspec for email validator

Fixes #5483
Add inverse_of for more associations involved in cart processing
Fixes #5488

Conflicts:
	core/app/models/spree/order.rb
	core/app/models/spree/tax_rate.rb

Conflicts:
	core/app/models/spree/return_authorization.rb
	core/app/models/spree/zone.rb
	core/app/models/spree/zone_member.rb
Add inverse_of for more associations involved in cart processing

Conflicts:
	core/app/models/spree/return_authorization.rb
	core/app/models/spree/zone.rb
	core/app/models/spree/zone_member.rb

Fixes #5489

Conflicts:
	core/app/models/spree/return_authorization.rb
remove extra dependent destroy
fixes #5492
Fix timecop spec.
Fixes messaging after applying coupon code promo with CreateLineItems action. Fixes #4697
Refactor Spree::ProductHelper#variant_price_diff

* Change the logic of the code to make it easier for the next
  commit.
* Remove duplicate code from the HTML generation.

Change #variant_price_diff to handle when the product amount is nil

Fixes #5493
Add required attributes to required product admin form fields

* Adjust spec example inputs to allow submit with that restrictions.

fixes #5496
make bogus gateway match actual gateways. ie. don't assign profile id for failed payments

fix handling of retry payments and multiple payments

fixes #5499