Test runtimes

Windows:
Running test Examples/Image/MNIST/02_Convolution (debug gpu) - [OK] 157.53 sec
Running test Examples/Image/MNIST/02_Convolution (release gpu) - [OK] 64.93 sec

Linux:
Running test Examples/Image/MNIST/02_Convolution (debug gpu) - [OK] 40.43 sec
Running test Examples/Image/MNIST/02_Convolution (release gpu) - [OK] 18.92 sec