link router (#99)

## Description
Removing linking specific API endpoints out of main and into
`recordlinker.routes.link_router`

## Additional Notes
This is just a code reorg change, no net new functionality has been
added.
- Create a new router for the linking API endpoints
- Create a new schema, `recordlinker.schemas.link` to store link
request/response payload signatures
- Remove `recordlinker.base_service` and define new names, versions,
descriptions for the Record Linker app in `recordlinker.main`
- renamed the FHIR api endpoint from `/link-record` to `/link/fhir`
- Removed the sample FHIR bundles for the FHIR endpoint

Author: ericbuckley