Deleted the continue button from adjustment index

On the adjustment index (in the admin) was a continue button.
The button only shows up on this page, it's a leftover from the old 'manual add an order' proces in the admin.

I deleted it.

Fixes #5395
Regression spec for 'stack level too deep' #5384

Fixes #5384
Add in fix from @andrzejpolis Fixes #5384 Fixes #5386
Fix example to contain expectation
Fixes #5449
allow guests to use the payments api for their orders
Fixes #5450
Improve localization of stock_locations/_form
Fixes #5454
Fix factories to generate unique SKUs

* Choosing random SKUs even from a high range can yield duplicates
  resulting in build failures.
* Kernel.rand(9999) was definitively never a good choice due the
  birthday paradoxon lets manifest a duplicate quite often
* Uses sequencially generated SKUs defined from a single shared and
  reusable generator.

Fixes #5452
Update dependencies

* updated kaminari, cancancan and Ransack
* fix product admin page:
  delete 'deleted_at_null' from the searchg query hash as now ransack behaves
  property and won't include products with null delete_at value

Fixes #5455

Conflicts:
	core/spree_core.gemspec
Bump 2.3.4
Bump to next beta.
Make create endpoint require important params

bit of clean up on these tests, but no more after #create

Fixes #5458

Conflicts:
	api/app/controllers/spree/api/shipments_controller.rb
Moving admin index route to bottom of routes file to allow it to be overridden without breaking pagination on the orders page

Fixes #5461
Update jquery-ui-rails

Fixes #5462
Add circle CI setup