Support reading a json array directly to a Java stream

[SingingBush]

Currently we have to get a collection then convert it to a stream:

final List<String> list = reader.read("$.store.book.[*].title", List.class);

final Stream<String> stream = list.stream();

it would be convenient to be able to do this directly:

final Stream<String> stream = reader.read("$.store.book.[*].title", Stream.class);

[SingingBush]

The solution in pull #829 seems reasonable to cover this requirement in a way that can be done across the different providers. I had a look at changing the GsonMappingProvider to achieve it by adding a TypeAdapter to the Gson config. As json-path doesn't expose a way to add an adapter I had to change the line where it instantiates Gson (return new Gson();) to instead be

final GsonBuilder builder = new GsonBuilder();

builder.registerTypeHierarchyAdapter(Stream.class, new TypeAdapter<Stream>() {
    @Override
    public void write(JsonWriter out, Stream value) throws IOException {
        throw new UnsupportedOperationException();
    }

    @Override
    public Stream read(JsonReader in) throws IOException {
        if (in.peek() == JsonToken.NULL) {
            in.nextNull();
            return null;
        }

        final List list = new ArrayList();

        in.beginArray();
        while (in.hasNext()) {
            switch (in.peek()) {
                case STRING:
                    list.add(in.nextString());
                    break;
                case NUMBER:
                    list.add(in.nextDouble());
                    break;
                case BOOLEAN:
                    list.add(in.nextBoolean());
                    break;
                case NULL:
                    in.nextNull();
                    break;
            }
        }
        in.endArray();

        return list.stream();
    }
});

return builder.create();

but this is still rather limited and I've still not looked at doing the same for Jackson. I opened #931 as it'll make it easier for the end user to implement something like this.