Add jmespath query language as another sepcification for querying json files

[otemek]

How about adding another json query specification language to be handled by this library? I'm thinking of something like:

    *** Settings ***
    Library    JsonLibrary    # by default it will be jsonpath_ng.ext

or by using jmespath as a backend json query specification

    *** Settings ***
    Library    JsonLibrary    jmespath    # just as an argument passed to initializer so this implementation will be used as a backend for querying json

such implementation won't be so hard, although there is some catch: if jmespath is used there won't be a possibility to manipulate json files (adding, deleting, modifying) as jmespath is a query language (imho more powerfull than jsonquery) and it does not handle any manipulations (...in an easy way, the hard way is waaay to hard - at least for me :)).

How about that?