Consider automatically registering Jackson modules

[mawis]

I think it would be helpful if Jackson modules found on the classpath could be loaded automatically. I especially think of the support for java.time.Instant that gets added when the jackson-datatype-jsr310 module is available.

I think that for this to work the defaultObjectMapperFactory in Validate.kt should call .findAndRegisterModules() on the generated ObjectFactory.

[cdimascio]

@mawis this is interesting. could you create a PR with what you're thinking. best!