Implement and document XML and JSON facades for /manage

[hunterhacker]

The /manage docs are light on what formats they return and accept back. We should make sure the user can specify and receive configuration info as XML or JSON, both, and have docs about it.

It may all be there and just needs documenting.

[ryangrimm]

Currently the /manage endpoints only offer output as JSON.

I can imagine some finding value in getting responses as XML, but it would be a fair amount of work and add complexity to some other issues like accepting a file that describes the entire configuration.

So while I think this is a good thing to have at some point, I'd rather spend the energy creating a friendly HTML front on top of the existing JSON endpoints first.