#50 - Only register LinkDiscoverer if JsonPath is on the classpath.
#50 - Add HAL JSON Module to handler adapters.

In case no ObjectMapper bean has been configured explicitly, the Spring MVC infrastructure registers HttpMessageConverters directly and does not declare them as Spring beans. Thus we now also inspect RequestMappingHandlerAdapter and AnnotationMethodHandlerAdapter instances for their HttpMessageConverters and transparently augment the ObjectMappers backing potentially registered Jackson converters.