No need to call gemspec in common_spree_dependencies

Each component Gemfile already calls it
Add index to source columns on spree_adjustments so UpdateAdjustmentStates migration does not take ages to run on large databases

Fixes #4145
Bump activemerchant to 1.42.3
Bump aws-sdk to 1.31.3
Update changelogs
Don't use hard coded assets prefix

Fixes #4156
Remove variant default_scope from Price class this fixes Price must belong to a variant when trying to fetch the price fo a deleted variant

Fixes #4169

Conflicts:
	core/spec/models/spree/variant_spec.rb
Prevents admin js errors by ensuring taxons key in api response

Fixes #4174
Improves Api::ProductsController#create
Fixes duplicate OptionTypes on Api::ProductsController#create
Fixes products_controller_spec
api/products variants spec shouldn't depend on order
Find or create shipping_category on api/products#create

Users can send a shipping_category string on the product payload and
spree will find or create that shipping_category and associate that
category with the product. e.g.

    product: {
      ...
      shipping_category: "Free Shipping Items"
    }
botsy insult Washington
Append omega to content classes

Fixes #4179
Order#available_payment_methods should also return payment methods marked as 'Both'

Fixes #4199
Add changelog for #4199
Bump acts_as_list to 0.3.0
Google analytics fix for IE8 SSL warning

Undoes #2977 which while cleaner in principle breaks IE8 SSL support.  I have verified this in my production app with a local override of `_google_analytics.html.erb`.

Fixes #4202
Reverts #2977
Ensure duplicate payment methods are not returned by Order#available_payment_methods