add java.util.Optional support

[ITurchenko]

Allow usage Optional<T>? in @QueryParam

data class OptionalRequest(
    @QueryParam("strictly optional", allowEmptyValues = true) val optInt: Optional<Int>? = null
)

Result
/request?optInt=1 > Optional.of(1)
/request?optInt= > Optional.empty()
/request?optInt=null > Optional.empty()
/request > null