Implement Vue routing

[chrabyrd]

We need to integrate Vue Router into the plugin to enable easy frontend navigation with browser history.

• Setup Vue Router
• Create and link routes to placeholder components
• Implement route lazy loading

There should be Hello world-level placeholder components for the welcome page, the user homepage, the search page, the advanced search page, and the Scheme list page.

An assumption with the time estimation of this ticket is that the pattern has been proven out in the Controlled List Manager and will largely be copy/pasted.