UX improvements for managed dashboards

Purpose:

Following implementation of managed dashboards there are some UX improvements to be made

1. Add an info pop over to the "Default" column header with the text: "The default dashboard is the one that will display by default when you first open the dashboard app"
2. On the Create/Edit dashboard page, the Cmd+S shortcut key should trigger "Save and close" (as with the create/edit widget page) and Esc should cancel/close the modal
3. In the Actions menu, add icons to each action and change the name of "Order widgets" to "Manage widgets"
   
4. If possible it would be good to give specific feedback to a user editing or deleting dashboards with multiple users
   1. On editing a dashboard to which multiple users have access, a warning should show "This dashboard is shared. Any changes made will be visible to all users with access." - see ERM-2314 for a mockup
   2. On deleting a dashboard to which multiple users have access, a warning should show "Deleting the dashboard <dashboard name> will remove access for one or more users. Select "Delete dashboard" to go ahead" see ERM-2314 for a mockup
   3. On saving the "User access" page and updates have been made, display a success callout with the text: "User access details updated: <dashboard name>"
5. Additional callouts for creation, update and deletion:
   1. On creating a new dashboard (selecting Save & close on the "New dashboard" form) display a success callout with the text "Dashboard created: <dashboard name>"
   2. On updating a dashboard (selecting Save & close on the "Edit dashboard" form) display a success callout with the text "Dashboard updated: <dashboard name>"
   3. On deleting a dashboard, display a success callout with the text "Dashboard deleted: <dashboard name>"
   4. On selecting Save & close on the "Manage dashboards" form and updates have been made, display a success callout with the text "Updates saved: Manage dashboards>"