Add HATEOAS sample application
Merge branch '1.1.x'
Fix HATEOAS sample application version number
Apply HATEOAS module to primary ObjectMapper

Update HypermediaAutoConfiguration to apply the Jackson2HalModule to
the primary ObjectMapper. This restores the behavior of Spring Boot
1.1 where HATEOAS types could be serialized for both `application/json`
and `application/json+hal` content types.

A `spring.hateoas.apply-to-primary-object-mapper` property has also been
provided to opt-out if necessary.

Fixes gh-2147