autodetection of input JSON format (dynamic jsonReader)

Hello Tony,

the poll request contains details of the changes which I posted in [the suggestion](http://www.trirand.com/blog/?page_id=393/feature-request/autodetection-of-input-json-format/) before.

It's clear the one can makes more optimization in `addJSONData` (for example one can remove unused second parameter `t`, remove `f` or at least replace it to boolean `f.length===0`, optimize the code by removing some duplicates in the code etc), but I wanted first to have just an implementation of autodetection feature. Optimization of the code can be done later.

Best regards
Oleg