webpack config - improvements

[ptrckvzn]

• removed .babelrc and move settings to webpack.config.js
• moved config.json to assets/config.json
• updated packages version
• fixed an issue of images and fonts not loading in chrome when running browsersync (publicPath value)
• went through sage 8 gulpfile.js to replicate its settings for image optimization, autoprefixer, etc. in webpack.config.js
• moved entries to config.json to allow easier addition of scripts and styles
• add bower_components to the list of module directories
• disabled source maps when calling webpack with '--release' to reduce compile time
• enable bootstrap 4 flex grid by default