Changes to keymaster as hotkey js lib. Fixes some (not all) of the hotkeys issues.
Removes the alt+w hotkey, dialogs can be closed with esc key.
Do not initialize Alchemy.Hotkeys after building elements and preview windows.

Events for Turbolinks page:update already handles this.
Changes link to latest RubyGems version.
Fixes creating of EssencePictures that are not inside of a picture gallery.

Cherry picked from 2.7-stable
Set add_new_content link to full width.
Ensures that essence#description always returns a Hash.

Cherry picked from 2.7-stable.
Adds spring app preloader to gem test and dev group.