Tech preview of compatibility layer for Spring Data REST

Requires productization of `quarkus-spring-data-rest`.

Upstream doc: https://quarkus.io/guides/spring-data-rest

Quickstart: https://github.com/quarkusio/quarkus-quickstarts/tree/master/spring-data-rest-quickstart

Known issues / limitations: 

• Only the repository methods listed in the doc are supported. No other standard or custom methods are supported

• Only the `exposed`, `path` and `collectionResourceRel` annotation properties are supported

Test coverage:

• Extension tests: https://github.com/quarkusio/quarkus/tree/master/extensions/spring-data-rest/deployment/src/test/java/io/quarkus/spring/data/rest
• Integration tests: https://github.com/quarkusio/quarkus/tree/master/integration-tests/spring-data-rest