Export non-routing types too

[davidlj95]

Currently, we export XMetadataRouteData so that you can write type-safe metadata objects. However, those types are for routes only. So when using metadata types that are not for routes, you don't have types for that.

For instance, when setting defaults:

https://github.com/davidlj95/chrislb/blob/8d9e6049154042c801a8efef30cc3be799979b12/src/app/app.module.ts#L45-L58

Or when calling the metadata service:

https://github.com/davidlj95/chrislb/blob/8d9e6049154042c801a8efef30cc3be799979b12/src/app/about-page/about-page.component.ts#L54-L56