Upgrade jQuery, jQuery UI, and SlickGrid to latest stable versions

[actapia]

These changes update jQuery, jQuery UI, and SlickGrid to the latest stable versions as of this writing (versions 3.7.1, 1.14.1, and 5.15.4, respectively) and make necessary changes to allow Emperor to work with the new versions, addressing part of #820 . The changes add Sortable.js (now a dependency of SlickGrid) and remove jquery-drag (no longer a dependency of SlickGrid).

These commits also remove a few Python test cases that require EMPeror to produce exact HTML, CSS, or JavaScript output, since these tests will fail any time one or more of the JavaScript dependencies is updated.