Remove System.out.println from PluginResource
Improve custom Swagger generator

* Add support for HEAD and OPTIONS
* Add support for method parameters with multiple annotations (e. g. javax.validation.*)
* Add support for HeaderParam and FormParam
* Remove superfluous Jackson PropertyNamingStrategy (see https://fasterxml.github.io/jackson-databind/javadoc/2.4/com/fasterxml/jackson/databind/PropertyNamingStrategy.html)
Superficial cleanup of JAX-RS resource classes
Clean up RestResource
Add Google AutoValue
Add value classes for REST API using AutoValue
Un-break MetricsResource
All ExceptionMappers generate response with ApiError
Improve error messages in IndicesResource
Fix deprecation warning for Guava Objects#firstNonNull
Merge branch 'rest-overhaul'