Changed calculate method to protected and virtual

Change-Id: I0e5900b4f079eee5f7b8933de2bf2f0a064cf762

wpilibc/wpilibC++/include/PIDController.h

@@ -103,7 +103,7 @@ private:
 	virtual void StopLiveWindowMode();
 protected:
 	ITable* m_table;
-	void Calculate();
+	virtual void Calculate();
 
 	DISALLOW_COPY_AND_ASSIGN(PIDController);
 };

wpilibj/wpilibJava/src/main/java/edu/wpi/first/wpilibj/PIDController.java

@@ -211,7 +211,7 @@ public class PIDController implements LiveWindowSendable, Controller {
      * This should only be called by the PIDTask
      * and is created during initialization.
      */
-    private void calculate() {
+    protected void calculate() {
         boolean enabled;
         PIDSource pidInput;