Aurelia 2 Update - Alpha 16

For the last month, since alpha-12, the focus of the Aurelia team has been v1 feature parity besides various bugs fixing, refactoring, performance & documentation improvements. The web-component plugin has been ported to v2. And web-components (WC) (custom)elements defined via Aurelia work independently with Aurelia components (elements), this enable mix-matching Aurelia components and WC elements together, enabling even more flexible, powerful & dynamic composition. The plugin also supports built-in element extensions, allowing simple HTML DOM. For the plugin documentation, visit https://docs.aurelia.io/developer-guides/web-components .