add default constructor for boost serialization

geometry/CalibratedCamera.cpp

@@ -10,6 +10,8 @@
 
 namespace gtsam {
 
+	CalibratedCamera()::CalibratedCamera() {}
+
 	CalibratedCamera::CalibratedCamera(const Pose3& pose) :
 		pose_(pose) {
 	}

geometry/CalibratedCamera.h

@@ -25,6 +25,7 @@ namespace gtsam {
 		Pose3 pose_; // 6DOF pose
 
 	public:
+		CalibratedCamera();
 		CalibratedCamera(const Pose3& pose);
 		CalibratedCamera(const Vector &v) ;
 		virtual ~CalibratedCamera();