Add HAL "Curies" for OpenHDS rels

[benjamin-heasly]

We should make our API "Discoverable" by using curies, as described here ("API Discoverability" near the bottom:
http://stateless.co/hal_specification.html

This would mean having a resource(s) that serves documentation. This would mean having documentation at all.

[benjamin-heasly]

Maybe we just serve documentation from openhds-rest, along side the REST API!

[benjamin-heasly]

Does Spring give us an easy way to serve easy-to-author static content like markdown?

[benjamin-heasly]

Spring HATEOAS supports HAL curies via its CurieProvider API: http://docs.spring.io/spring-hateoas/docs/current/reference/html/#spis.curie-provider

[benjamin-heasly]

Let's say there are two parts to this:

1. figure out how to author and serve static docs from openhds-rest, along side the REST API.
2. add a HATEOAS CurieProvider to integrate HATEOAS links with the docs.

Let's give about 1 day for each of those.

This issue is separate actually authoring the documentation. See #118 .

[benjamin-heasly]

Example of serving markdown with Spring Boot.
https://github.com/jetaggart/spring-boot-markdown

[benjamin-heasly]

17633c9 adds markdown documentation and serves it from /documentation/foo

[benjamin-heasly]

See deployed example: https://arcane-lake-8447.herokuapp.com/documentation/registration-use-cases