Scaffolding for import progress reporting
Route ajax request to appropriate view, and show feedback only then

Hook up view

Fix getStatus function
Studio: revises general layout/styling of import view and adds in detail progress feedback after import (WIP)

Studio: removes import progress bar HTML and Sass; hides import status by default

Studio: revises import file upload success copy; sets up showing/hiding states for import status and additional messages

Studio: revises iconography and adds in success step in import status feedback

Studio: adds hidden styling back into import status UI
Hook up js to css classes
Use swanky error css for error messages
Studio: revises import view Sass extends to use placeholder syntax
Remove references to old upload progress bar
Re-add bar references
Studio: adds in action-related elements to the status display UI of the Import view
Studio: copy and styling changes to import view to support new status UI
Clear import status on retry
Review fixes

Studio: revises import help/status copy to better reflect/generalize what is done with imported content

Add test cases for import status
Move import-related js to import.js
Update changelog
Studio: adds in instructional copy to user on when it is safe to leave the import view without harming an import process
Use requirejs for import.js

    And fixes for rebase-breakage.
Merge pull request #1043 from edx/jkarni/feature/import-feedback

Jkarni/feature/import feedback