main: Stop importing patternfly.css

* Stop importing cockpit's base1/patternfly.css

This is deprecated API and will be dropped at some point, in favor
of projects shipping their own CSS.

Install and import the styles from PF4 now.

* Use webpack based string replacement for removing the font-face rules from PF4

Doing the seddery in Makefile breaks `npm run build`, webpack watching,
and is generally brittle.
Do the font replacement hacking with `string-replace-loader`, which fits into webpack much more nicely.

There is still some potential simplification by not duplicating the
entire scss loader chain.

Co-authored-by: Martin Pitt <martin@piware.de>

Closes #315

src/index.js

@@ -17,11 +17,21 @@
  * along with Cockpit; If not, see <http://www.gnu.org/licenses/>.
  */
 
+import "./lib/patternfly-4-cockpit.scss";
+
 import "core-js/stable";
 
 import React from 'react';
 import ReactDOM from 'react-dom';
 import { Application } from './app.jsx';
+/*
+ * PF4 overrides need to come after the JSX components imports because
+ * these are importing CSS stylesheets that we are overriding
+ * Having the overrides here will ensure that when mini-css-extract-plugin will extract the CSS
+ * out of the dist/index.js and since it will maintain the order of the imported CSS,
+ * the overrides will be correctly in the end of our stylesheet.
+ */
+import "./lib/patternfly-4-overrides.scss";
 
 document.addEventListener("DOMContentLoaded", function () {
     ReactDOM.render(React.createElement(Application, {}), document.getElementById('app'));