Display a "Name on card" input on payment step

It creates a name column on spree_credit_cards table to insert the data
instead of using the old first_name and last_name fields, fixes #2486
Move payment partial from core to frontend

Plus make it use the name attribute instead of the deprecated first_name
and last_name
Add CHANGELOGs entries for payment name on card feature
there is a conflicting migration in 2-1-stable branche (8de75a5d3d519c5498843edda983702852caaade)
it's order_id ofcourse!
Make Stock::Package more aware of units structure

`add` and `find_item` now might receive a variant and a line item for
cases where they both don't refer to the same product
Grab shipment line items via inventory units

The previous implementations doesn't make sense anymore on the current
split shipments scenario. Can't see a reason why tracking inventory
levels config should influence whether or not the line item should be
returned
Load line items in shipment `manifest`

We still need to figure out a way to lazy load inventory units variant
and line items removing the default scope from Variant
Add inverse_of to product variant associations

Fixes #4031
added autocomplete off HTML5 tag to mail method settings for username and password

Fixes #4036
stock_movements helper fix for stock_transfer

Fixes #4037
Only restock on_hand inventory units

Example: Spree restocks items once you cancel an order. However it
shouldn't add stock (restock) items from backordered inventory units.

Conflicts:
	core/spec/models/spree/shipment_spec.rb
Restock items but dont process backorders for canceled orders

Fixes possible issue where canceling an order with backordered inventory
units would make other orders inventory transition from backordered to
on_hand. e.g.

    - create two separate orders of the same item at the same stock location
    - both orders will have shipment state of backorder
    - cancel one of the orders
    - the second order inventory will transition from backorder to ready

Now the second order inventory remains backorder
Downcase inventory unit state in manifest partial
Only showing unique order records if searching on attributes of associated models like bill_address or line_items

Fixes #3919
Only respond with js if .xhr? is true

Prevents user private data leak for GET requests from other domains
See discussion on rails-core mailing list
https://groups.google.com/forum/#!topic/rubyonrails-core/rwzM8MKJbKU
Remove duplicated product method

Fixes #4042
Consider both line item and variant when removing iu

Applications and extensions might set up inventory units where line item
and variant does not refer to the same product. By matching both when
removing inventory we make sure that the right inventory units are
always removed. It follows the same logic already implemented when
inventory units are create via the same OrderInventory class
Improve method naming for OrderInventory
Fix frontend features locale_spec

It failed with:

     ActionView::Template::Error:
       undefined method `content_tag' for Spree:Module

Probably due to recent changes in rails i18n api related to the security
patch in 4.0.2, see https://groups.google.com/forum/#!topic/ruby-security-ann/pLrh6DUw998
and https://github.com/rails/rails/commit/78790e4bceedc632cb40f9597792d7e27234138a