Resolve "StateBlock perturbation helper function for gtests"

Closes #275 (closed)

include/core/state_block/state_block.h

@@ -142,6 +142,10 @@ public:
          **/
         void resetLocalParamUpdated();
 
+        /** \brief perturb state
+         */
+        void perturb(double amplitude = 0.1);
+
         /** \brief Add this state_block to the problem
          **/
         //void addToProblem(ProblemPtr _problem_ptr);