IVGCVSW-3418 Add Arm NN front end support for the new Stack layer

 * Added new StackLayer class
 * Made necessary changes to Descriptors, ILayerSupport, ILayerVisitor, etc.
 * Added unit tests

Signed-off-by: Matthew Jackson <matthew.jackson@arm.com>
Change-Id: Ieb97a928a342ffe1901c6058eb895711c358fd3d
diff --git a/CMakeLists.txt b/CMakeLists.txt
index dc34b1a..7c163dc 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -312,6 +312,8 @@
     src/armnn/layers/SpaceToDepthLayer.cpp
     src/armnn/layers/SplitterLayer.hpp
     src/armnn/layers/SplitterLayer.cpp
+    src/armnn/layers/StackLayer.hpp
+    src/armnn/layers/StackLayer.cpp
     src/armnn/layers/StridedSliceLayer.cpp
     src/armnn/layers/StridedSliceLayer.hpp
     src/armnn/layers/SubtractionLayer.cpp