Invalid configuration object. Webpack has been initialised using a configuration object that does not match the API schema

I have this simple helloworld react app created from an online course, however I get this error:

Invalid configuration object. Webpack has been initialised using a
configuration object that does not match the API schema.
 - configuration has an unknown property 'postcss'. These properties are valid:    object { amd?, bail?, cache?, context?, dependencies?,
devServer?, devtool?, entry, externals?, loader?, module?, name?,
node?, output?, performance?, plugins?, profile?, recordsInputPath?,
recordsO utputPath?, recordsPath?, resolve?, resolveLoader?, stats?,
target?, watch?, watchOptions? }    For typos: please correct them.   
For loader options: webpack 2 no longer allows custom properties in
configuration.
     Loaders should be updated to allow passing options via loader options in module.rules.
     Until loaders are updated one can use the LoaderOptionsPlugin to pass these options to the loader:
     plugins: [
       new webpack.LoaderOptionsPlugin({
         // test: /\.xxx$/, // may apply this only for some modules
         options: {
           postcss: ...
         }
       })
     ]
 - configuration.resolve has an unknown property 'root'. These properties are valid:    object { alias?, aliasFields?,
cachePredicate?, descriptionFiles?, enforceExtension?,
enforceModuleExtension?, extensions?, fileSystem?, mainFields?,
mainFiles?, moduleExtensions?, modules?, plugins ?, resolver?,
symlinks?, unsafeCache?, useSyncFileSystemCalls? }
 - configuration.resolve.extensions[0] should not be empty.

My webpack file is:

```
// work with all paths in a cross-platform manner
const path = require('path');

// plugins covered below
const { ProvidePlugin } = require('webpack');
const CopyWebpackPlugin = require('copy-webpack-plugin');
const HtmlWebpackPlugin = require('html-webpack-plugin');

// configure source and distribution folder paths
const srcFolder = 'src';
const distFolder = 'dist';

// merge the common configuration with the environment specific configu

I don't exactly know what causes that, but I solve it this way.

Reinstall whole project but remember that webpack-dev-server must be globally installed.
I walk through some server errors like webpack cant be found, so I linked Webpack using link command.
In output Resolving some absolute path issues.

In devServer object: inline: false

webpack.config.js

module.exports = {
    entry: "./src/js/main.js",
    output: {
        path:__dirname+ '/dist/',
        filename: "bundle.js",
        publicPath: '/'
    },
    devServer: {
        inline: false,
        contentBase: "./dist",
    },
    module: {
        loaders: [
            {
                test: /\.jsx?$/,
                exclude:/(node_modules|bower_components)/,
                loader: 'babel-loader',
                query: {
                    presets: ['es2015', 'react']
                }
            }
        ]
    }

};

package.json

{
  "name": "react-flux-architecture-es6",
  "version": "1.0.0",
  "description": "egghead",
  "main": "index.js",
  "scripts": {
    "start": "webpack-dev-server"
  },
  "repository": {
    "type": "git",
    "url": "git+https://github.com/cichy/react-flux-architecture-es6.git"
  },
  "keywords": [
    "React",
    "flux"
  ],
  "author": "Jarosław Cichoń",
  "license": "ISC",
  "bugs": {
    "url": "https://github.com/cichy/react-flux-architecture-es6/issues"
  },
  "homepage": "https://github.com/cichy/react-flux-architecture-es6#readme",
  "dependencies": {
    "flux": "^3.1.2",
    "react": "^15.4.2",
    "react-dom": "^15.4.2",
    "react-router": "^3.0.2"
  },
  "devDependencies": {
    "babel-core": "^6.22.1",
    "babel-loader": "^6.2.10",
    "babel-preset-es2015": "^6.22.0",
    "babel-preset-react": "^6.22.0"
  }
}

Stack Overflow Q#42060243, score: 34