selector: Add Intern unit and functional tests

Includes a utility module with a method for detecting shift+click support,
since it doesn't seem to work through WD with certain versions of IE and FF.
Tests involving shift+click are no-ops in these browsers.
selector: unit and functional test cleanup

* Add test suites to all.js and functional.js
* Add proper teardown and fix formatting in unit test
* Test allowSelect rather than disabled, since the two are redundant and
  disabled will eventually be discontinued
* Remove unnecessary waitFor* calls
* Pass functions to remote.execute calls, not strings
* Make isShiftClickSupported return a boolean for easier use
* Refactor control flow to only call isShiftClickSupported once
* Remove questionable/unsupported case of allowSelectAll + single selection
* Remove unused debugging code
* Chain calls where it doesn't hinder readability
Move functional test utilities into functional folder