MDL-66109 js: Upgrade Node dependencies
This change updates most libraries used in our Grunt build stack and applies necessary changes to Grunt and Gherkin-lint configuration to ensure that they continue to work. The grunt-sass plugin has been updated to support alternative 'implementations' of sass compilers, and the chosen sass compiler must now be specified in the grunt configuration. We continue to use the `node-sass` package for this. Our gherkin-lintrc included two rules which were renamed from 'no-unamed-*' to 'no-unnamed-*'. This change occurred in version 2.0.0 of Gherkin-lint and has no other effect.