Inlining resources and generator improvements

New features

• Inlining of JavaScript and stylesheet files is now supported with LoadMode.INLINE
• Generated components now support slots
• webcomponents-loader is now being used instead of the full set of WebComponent polyfills
• Generated components now automatically add the @Synchronized annotation to getters which are mapped to change events

Fixes

• Vaadin Push JavaScript dependency is now served correctly in production mode

Tutorials

• Added description for the afterServerUpdate client-side method

All changes

https://github.com/vaadin/flow/milestone/39?closed=1