Build Levels page now has links to the pages listing all artist & non-artist levels, just for convenience.
Use Railsy stuff to generate links to levels for content authors.
Merge pull request #919 from code-dot-org/authoringlinks

Build Levels page now has links to the pages listing all levels.
Change learn.code.org Google Analytics back to use main code.org property ID.
Merge branch 'finished' of github.com:code-dot-org/dashboard into finished
Merge branch 'finished' into delivered