[632] ⚡️ Upgrade to Vue 2.3.x

Hello guys. I've opened this one trying to help making upgrade progress faster. Feel free closing if you are internally working on this. Following list is according to 2.3.0 release notes and new dedicated Vue SSR guide.

• Allow runInNewContext option. which can bring huge performance improvement in production.
• vue-ssr-webpack-plugin is deprecated. (webpack plugins)
• Generating clientManifest
• Vue 2.3.x broke middleware in dev #636 (seems working)
• Duplicate assets in client manifest entry point
• CI Fails with infinity wait with new vue-loader (12.x)
• server side directives
• New CSS Management