Fix Spree.translations corruption of I18n cache

Fixes #2711
Mailers now require a from address, so we need to give defaults, using MailMethod.current
Correct MailMethod usage in mail_interceptor, order mailer and shipment mailer specs

Conflicts:
	core/spec/mailers/shipment_mailer_spec.rb
Invoke callbacks in #create and #update

Fixes #2736
Correct filename for diners club credit card icon

Fixes #2726

Conflicts:
	frontend/app/assets/images/credit_cards/icons/diners_club.png
Remove the bulk of SSL handling code in favor of default Rails "force_ssl" config option

Conflicts:
	core/lib/spree/core/ssl_requirement.rb
Process processable payments as soon as possible outside any transaction
Fix route in Admin::PaymentsController
Pagination of Orders in Admin loses date range when only showing complete orders

As date params are deleted if @show_only_completed is true,
store the original date so we can restore them into the params
after the search

[Fixes #1724]
Remove deprecated ssl_required and ssl_allowed
Update selenium so we can use Firefox 19
Use user_search_basic for user auto-completion