Add basic tutorial to designer:
  set ?tutorial=1 to enable
  content isn't completely accurate
  no element highlighting/modal backdrop yet
  styles not fully developed
Fix intro tutorial content path for text require
Add built files
Add newline at end of file
Remove duplicate variable declaration
Corrections from PR review
Replace tutorial content id attributes with data-step, and simplify linking js step to its content
Reuse control definition across steps, include a done button at end
Merge pull request #1734 from mozilla-appmaker/1512-tutorial

Intro tutorial