Implement a sub-framework for easier JSON processing and validation

[ipolevoy]

goals:

1. easy to pick and chose parts of JSON by using direct links: "university.students.joe".
2. Implement the use of the validation framework to allow declarative validations:

JSONRequest r = new JSONRequest(String json){
   validatePrecenseOf("university.students.joe");
   validateNumericalityOf("university.students.joe.age");
... and so on
}

This way, processing and validation of JSON requests in ActiveWeb will become easier.