Add learner_url to interactive_run_states (start of [#64338848])

When LARA loads an interactive using saved student data, it uses the versioned URL returned by Lab.

https://www.pivotaltracker.com/story/show/64338848
Sometimes use the LearnerURL for displaying interactive

[#64338848]

When LARA loads an interactive using saved student data, it uses the
versioned URL returned by Lab.  This commit checks to see if there is
a learner_url, and uses that if it exists.

https://www.pivotaltracker.com/story/show/64338848
Add a button to ‘Undo all my work’ – reloads authored Interactive.

[#64338848]

We need a way for students to restart their work from a fresh Interactive.
TODO:  I suspect we need to talk about the button label, and alert text.

https://www.pivotaltracker.com/story/show/64338848
Rename font-awesome styles to get the menu down arrow to show up again.

Also restores the camera, check-mark and other icons.

See: https://github.com/FortAwesome/Font-Awesome/wiki/Upgrading-from-3.2.1-to-4

[#63832956]
https://www.pivotaltracker.com/story/show/63832956
Don't validate when duplicating or re-ordering pages.

[#64347858]
https://www.pivotaltracker.com/story/show/64347858
interactive_page.rb : save without validation when duplicating.

[#64347858]

https://www.pivotaltracker.com/story/show/64347858
Merge branch 'staging' into production

* staging:
  interactive_page.rb : save without validation when duplicating.
  Don't validate when duplicating or re-ordering pages.
  Rename font-awesome styles to get the menu down arrow to show up again.
  Add a button to ‘Undo all my work’ – reloads authored Interactive.
  Sometimes use the LearnerURL for displaying interactive
  Add learner_url to interactive_run_states (start of [#64338848])