Refactored passing questiontype use objs/json

Refactored the code so that Objects can be used to manage questiontypes
(adding a new question type means just creating a new class and
inheriting from questiontype, meaning it's easier to extend). For this,
encoding and decoding the object into a json string was necessary, so it
could be passed from the view back to the controller.
Reinstalled Json.NET

Previous installation was causing an exception to be thrown when unit
testing causes the faux-failure of two unit tests. Reinstalling through
nuget Update-Package fixed problem.