Current target: Start with a user case: deciding if a given text
attribute contains question mark for all cases;
source code in SNMLToolkit: usercase.markquestion

Finished part for this commit: Json files convert to Arff file, with a
txt keeping the jsonFile name + instanceIndex in ArffFile

json reference changed from json-lib to
http://mvnrepository.com/artifact/org.json/json/20131018
User case: simply tag instances with question mark or not
finished, tested
User can implement the Marker interface like QuestionMarker to define
their own rules.