Improve routing to support passing arguments

[rolznz]

Wait until there is a valid usecase for this. One possible way:

In src/components/routes.ts each route could take params: (params) => <some-component invoice={params.invoice}/>

In src/components/bc-router-outlet.ts: r = routes[this._route](this._routeParams); // this._routeParams comes from the store

In src/state/store.ts: pushRoute: (route: Route, params: FixMe) => {