fixes #13244 - update Rails to 4.2.6

- Add responders gem to support class-level respond_to usage
- http://edgeguides.rubyonrails.org/4_2_release_notes.html#respond-with-class-level-respond-to
- Replace foreigner with native Rails 4.2 FK support
- uses a patch from Rails 5 to support Foreigner's...

fixes #14415 - check CR availability with Fog, not SETTINGS

Simplifies the code for checking compute resource availability, which
can easily be determined with the registered Fog providers instead of
being stored in SETTINGS in app initialisation. Plugins should always be...

fixes #12746 - list compute resources from plugin definitions

Load the full list of known CRs from plugins on the fly, instead of
modifying the class-level list of supported plugins. Since plugin
definitions don't get reloaded, this allows the ComputeResource class to...

Fixes #13727 - Error raised when setting default_value when override is set to false

fixes #14338 - move session store configuration earlier

When a plugin has an initializer relying on :build_middleware_stack, the
middleware stack is constructed with the default session store (cookies)
as the store hasn't been configured by config/initializers/ yet. Moving...

fixes #14318 - load JS translations table for current locale only

fixes #14225 - add missing require for Resolv

Setting itself is explicitly required too, which will provide a better
error message in future for this and similar issues loading the class.

Fixes #14071 - Using Sprockets directive to require host_edit_interfaces.js

fixes #13878 - handle anonymous railtie classes seen on Rails 4.2

fixes #13804 - set enforce_available_locales in app config

Rails 4.1.9 in rails/rails@4399a23 sets I18n.enforce_available_locales
to the value in the Rails app config, which now defaults to true,
overwriting the false value set in the initialiser. Set it in the app...