Add method to store a variable from a response field found by json path

[vboldor]

/**
* Stores the value of the response field found by json path
/
this.Then(/^(api) user stores the value '(.)' from response in variable (.*)$/, function(keyPath, name, callback) {

   keyPath = helperCommon.getTreatedValue(keyPath);
   var varName = helperCommon.getTreatedValue(name);

   //get value from JSON using JSONPATH
   jsonparser.init(trest.response.body);
   var varValue = jsonparser.getValue(keyPath)[0];

   // Add the value to variables
   helperVars.addVariable(varName, varValue);
   this.delayCallback(callback);

});