Add support for injecting Optional<T> parameter types

Currently, PathParam and QueryParam support the following construct (from https://docs.jboss.org/resteasy/docs/3.0.17.Final/userguide/html_single/#_PathParam):

The parameter type you inject into can be any primitive type, a String, or any Java object that has a constructor that takes a String parameter, or a static valueOf method that takes a String as a parameter.

Proposal is to also support java.util.Optional.ofNullable as a wrapper object for Strings, which is always called. This will eliminate all null checks for optional parameters in resource classes with the different Optional followup methods, such as optional.ifPresent.