Add autoconfig support for Jersey (2)

Jersey 2 has some Spring support built in but it's a bit awkward to
use in a Boot app, so autoconfiguration seems appropriate. The tests
and sample show how to use it, but the short story is that any
@Component can define JAX-RS endpoints via @GET etc.

There's a sample for Jersey 1 as well (pay careful attention to
the plugin configuration if you want to build an executable jar)

Fixes gh-1651