Fixes #32584 - drop flot charts

All uses of flot charts have been deprecated and are rendering React
counterparts. We can remove flot charts now.

Fixes #29331 - use patternfly v4 fonts

Fixes #16294 - Remove noVNC from vendors

fixes #14178 - introduce patternfly toast notifications

- replaces old jnoitfy with react implementation.
- Adds a notification store to handle events from
rails flash + legacy javascript Notice function and expose
an Action API to add notifications.

Fixes #16286 - Move multiselect from gem to npm

Fixes #13936 - Drop support for legacy browsers

This patch removes various workarounds needed to get legacy browsers to
work. Mostly stuff needed for IE<10, but also some other vendor prefixes
that are no longer needed.

Fixes #16293 - Move vendored diff.js to webpack (#3784)

Also removed a few outdated lines from the LICENSE file.

Fixes #13047, #16291 - Upgrade datatables and move it to npm

fixes #16089 - replace flot-rails with npm jquery-flot

Fixes #12364 - Use NPM+Webpack to handle external assets

This commit introduces NPM and Webpack to handle external assets.
It also provides ES6 support and a live reload dev server that can be
used by running `foreman start` instead of `rails start`.
Do not forget to run `npm install` before starting the server....