De/serialize POD objects

[rjframe]

We should de/serialize objects to JSONValue rather than require the caller to do so ahead of time.

[rjframe]

This can now be done explicitly: client.call("func", mystruct.serialize);

I want to allow implicit serialization before closing this: client.func(mystruct);

[rjframe]

Note: this only works for the client. The server isn't ready yet.

Also, spoke too soon; sometimes this will be fine, other times there's an access/visibility issue.