sets up variable_questions_spec
adds tests for variable question data
moves VariableReassignment prompt and input eval to initialize method
moves DataStructureAccess prompts and inputs eval into respective initialize methods
moves DataStructureAssignment prompts and input evals into respective initialize methods
moves MethodDefinitionQuestion's prompt and input eval to initialize method
moves MethodInvocationQuestion's prompt and input eval into initialize method
moves NestedDataStructureAccessQuestion's prompt and input eval into initialize method