registered ConfirmationsController
Add application config option to remove breadcrumb
added confirmations views to views/active_admin/devise
added translations for resend confirmation instructions for available languages by devise-i18n-views gem
Resources can override app breadcrumb config
fix decorator bug -- resolves #2886
code style update
Merge pull request #2889 from quainjn/remove_breadcrumbs

Add application config option to remove breadcrumb
Merge pull request #2887 from jitendra/fix-resend_confirmation_view

registered ConfirmationsController to fix resend confirmation view
provide a nicer `to_s` if no preferred display name is defined
display_name spec cleanup

note that our use of `subject{ }` here was incorrect -- the subject
returned was actually the `"display_name"` string from the parent
`describe` block :<
add tests and update the display_name fallback behavior