Minor improvement to Size, Duration, make jackson serializable

[cowtowncoder]

I noticed that two types, Size and Duration, are not by default serializable with Jackson. But it looks like 'toString()' method would work well, so the fix would be as simple as adding @JsonValue for 'toString()' methods. I assume this is ok since there is already @JsonCreator used; otherwise we could almost as easily create custom serializers, which is what I do locally.

My specific use case is debugging: I just want to print out Configuration object as JSON during startup.

Related to this, I guess it might be also useful to expose config object itself via GUI (similar to /threads etc); but I leave that for future improvements. :-)
(further ahead, really trying to dig into Jetty setup, JMX exposes only subset... but I digress).

Let me know if you want a patch (I realize that a unit test would be good, esp. for round-tripping); fix itself is trivial.

[codahale]

I'd absolutely merge a patch for this.

[cowtowncoder]

:-D

Ok, I'll add annotations first. On admin page(s): where do things like /threads get wired in? I #fail'd to find it.

[codahale]

Those are in Metrics, actually.

[cowtowncoder]

Ok. Makes sense, one of the paths did lead there...

[codahale]

Fixed in 9c8b7d7.