JSON: make the response configurable, set encoding

JSON: make the response configurable, set encoding

add request parameter 'i' and 'd'
if i=y, indent the output to make it human readable
if i is missing or anything else, send the output unformatted to save bandwith

'd' defines recursion depth with a default of 1 to show the requested node
and the immediate childs (if it has any)

call /json/?i=y&d=999 for a complete property tree backup (use with caution!)

Also set the encoding to UTF-8 as required per RFC 4627