create a has and belongs to many association for spree taxons and prototypes

add taxons for admin prototypes

add spec to prototypes feature for deleting

remove old `.find_all_by_prototype` code

This code seems old. It is trying to do a table join on a non-existent
relationship, or rather, a table that is non-namespaces with `spree_`.
Also, I couldn’t get it working while writing tests for it. Tested out
the method on a current project and returned PG errors. Tests returned
SQLite errors.

Fixes #5476
Remove shoulda matchers again.
remove top and bottom pixels from admin nav
fixes #4924
create proposed shipments if is no shippment data
also make sure to set the cost provided after order update

Conflicts:
	core/lib/spree/core/importer/order.rb
	core/spec/lib/spree/core/importer/order_spec.rb
Looking up stock location by the admin name as well

fixes #5484
Add spec for looking up stock location by admin name.
Remove spec invalidated by https://github.com/spree/spree/commit/a13524a6cfd363c441ff1607a584a3be07e1124f now creating shipments.
Do not allow leading or trailing dot(.) in the first part of email address

Add rspec for email validator

Fixes #5483
Simplify set_current_order. Fixes #5382
Search for guest order first before running Order.new

Fixes #5441
Add inverse_of for more associations involved in cart processing
Fixes #5488
Loosen kaminari dep. Fixes #5486
Fix guides links.
rspec-retry is just a test dependency.
remove extra dependent destroy
fixes #5492