jQuery UI is no longer used anywhere so say goodbye to it from package.json & Gemfile

see: https://docs.npmjs.com/misc/semver

See https://github.com/stefanpenner/es6-promise/issues/100

```
[WDS] Warnings while compiling.
./vendor/assets/javascripts/es6-promise.auto.js
Module not found: Error: Can't resolve 'vertx' in
'/Users/eric/Documents/gitlab/gitlab-development-kit/gitlab/vendor/assets/javascripts'
 @ ./vendor/assets/javascripts/es6-promise.auto.js 140:16-26
 @ ./app/assets/javascripts/application.js
 @ multi (webpack)-dev-server/client?http://localhost:3808
./application.js
```

This reverts merge request !9044

Part of #18437 to remove jQuery UI. This removes the datepicker

Add the following line to GDK Procfile to play with it:

    webpack: exec support/exec-cd gitlab npm run dev-server

Change airbnb eslint config package to `eslint-config-airbnb-base` and update plugins.

Change `airbnb` to `airbnb-base` for .eslintrc `extends` value.

Added changelog entry

Made sure all plugins and envs are set

Corrected new failing specs