COMPMID-2452: Add mnist example

* Add small-mnist example
* Add PrintAccessor
* Add DequantizationLayer graph node

Change-Id: I7bc8011e5a602f40fa3c47b231a2a69c804e78c2
Signed-off-by: Isabella Gottardi <isabella.gottardi@arm.com>
Reviewed-on: https://review.mlplatform.org/c/2274
Comments-Addressed: Arm Jenkins <bsgcomp@arm.com>
Tested-by: Arm Jenkins <bsgcomp@arm.com>
Reviewed-by: Giorgio Arena <giorgio.arena@arm.com>
Reviewed-by: Georgios Pinitas <georgios.pinitas@arm.com>
diff --git a/arm_compute/graph/nodes/NodesFwd.h b/arm_compute/graph/nodes/NodesFwd.h
index 53f2a6a..42fe0d0 100644
--- a/arm_compute/graph/nodes/NodesFwd.h
+++ b/arm_compute/graph/nodes/NodesFwd.h
@@ -39,6 +39,7 @@
 class ConvolutionLayerNode;
 class DeconvolutionLayerNode;
 class DepthwiseConvolutionLayerNode;
+class DequantizationLayerNode;
 class DetectionOutputLayerNode;
 class DetectionPostProcessLayerNode;
 class DummyNode;