Adding Gson annotations to the Page<T> object to make it serialize nicely

[wasperen]

I am working on a set of Nifi - CouchDB processors. Using the Page mechanism to chunk results up in a set of smaller FlowFiles.

Rather than create my own "Page"-like object, I would like to annotate your Page class such that it serializes nicely. My idea is to make the nextParam a transient field and define lower case with underscore alternative names for the other fields.

I'll create a pull request to show what I mean.