Make print() const

include/IMU/processor/processor_IMU.h

@@ -20,7 +20,7 @@ struct ProcessorParamsIMU : public ProcessorParamsMotion
     {
         //
     }
-    std::string print()
+    std::string print() const
     {
         return "\n" + ProcessorParamsMotion::print();
     }

include/IMU/sensor/sensor_IMU.h

@@ -40,7 +40,7 @@ struct IntrinsicsIMU : public IntrinsicsBase
         ab_rate_stdev       = _server.getParam<Scalar>(_unique_name + "/ab_rate_stdev");
         wb_rate_stdev       = _server.getParam<Scalar>(_unique_name + "/wb_rate_stdev");
     }
-    std::string print()
+    std::string print() const
     {
         return "\n" + IntrinsicsBase::print()                           + "\n"
             + "w_noise: "           + std::to_string(w_noise)           + "\n"