[WIP]Fixed #16193 -- Added qunit to test javascript.

Added qunit tests to test suite. Currently needs more tests to be written. Uses node and grunt to run the test suite from the command line with phantomjs. Uses jshint for linting.

 - [ ] Fix jshint errors.
 - [ ] Add missing tests.

This doesn't fix the more general problem of javascript testing any django application, but it does at least allow us to unit test most of the admin javascript.
This file also uses both 4 space and 2 space indentation.

Maybe we should add a `.editorconfig` and use the same style in these new files as in the rest of Django?

Example: https://github.com/treyhunner/django/blob/enforce-code-style/.editorconfig