parent-message-api.js : add message support for get/set LearnerUrl.

[#64338690]

This allows us to get a nice URL for loading learner data
into a pinned version of lab.

https://www.pivotaltracker.com/story/show/64338690
url-helper.js : formatting (whitespace) and add protocol to URL.

[#64338690]

https://www.pivotaltracker.com/story/show/64338690
application.js application.html.haml: Example use of getLearnerUrl

[#64338690]

https://www.pivotaltracker.com/story/show/64338690
Merge branch 'master' into versioned_urls

* master:
  ignore redirecting interactives
  add 3 redirects for InquirySpace