[PCollections] jackson-datatype-pcollections is missing serializers

[mateusz-bajorek]

As in the topic, PCollections support in jackson is missing serializers for TreePVector, MapPSet and others. From the module class:

@Override
public void setupModule(SetupContext context)
{
    context.addDeserializers(new PCollectionsDeserializers());
}

[cowtowncoder]

Indeed. If anyone is interested in adding support, would love to help get PRs merged.