Adds ctrl/cmd+s shortcut to whole application with a noop default

closes #4516
- shortcut for ctrl/cmd+s on application level
- shortens a syntax for any route that is using 'save' method, shortcuts object doesn't have to be defined at all, only the save action.
Again, don't need.

The way `send` works is, the action first gets sent to the leaf controller, then passed up to its route, then up the route heirarchy. That means even if a high-level route (like application) sends an action, all of its children get to handle it first.