IVGCVSW-4496 Add Flatten support to ONNX parser

 * Added ParseFlatten method
 * Added Read int64 attribute method
 - Modified ComputeReshapeInfo method
 - Modified ParseReshape
 * Added unit tests
 - Reorganised OnnxParser.cpp/.hpp

Signed-off-by: Ryan OShea <Ryan.OShea2@arm.com>
Change-Id: I8a9553438dd1e8c702d821b093587e0074c027d5
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 9e31a03..20e8717 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -820,20 +820,21 @@
 
     if(BUILD_ONNX_PARSER AND ARMNNREF)
         list(APPEND unittest_sources
-            src/armnnOnnxParser/test/Constructor.cpp
-            src/armnnOnnxParser/test/CreateNetwork.cpp
-            src/armnnOnnxParser/test/ProtoxtFixture.cpp
+            src/armnnOnnxParser/test/Addition.cpp
+            src/armnnOnnxParser/test/BatchNorm.cpp
             src/armnnOnnxParser/test/Clip.cpp
             src/armnnOnnxParser/test/Const.cpp
-            src/armnnOnnxParser/test/Pooling.cpp
-            src/armnnOnnxParser/test/Reshape.cpp
-            src/armnnOnnxParser/test/Relu.cpp
+            src/armnnOnnxParser/test/Constructor.cpp
             src/armnnOnnxParser/test/Conv2D.cpp
-            src/armnnOnnxParser/test/Addition.cpp
+            src/armnnOnnxParser/test/CreateNetwork.cpp
+            src/armnnOnnxParser/test/DepthConv.cpp
+            src/armnnOnnxParser/test/Flatten.cpp
             src/armnnOnnxParser/test/FullyConnected.cpp
             src/armnnOnnxParser/test/GetInputsOutputs.cpp
-            src/armnnOnnxParser/test/BatchNorm.cpp
-            src/armnnOnnxParser/test/DepthConv.cpp
+            src/armnnOnnxParser/test/Pooling.cpp
+            src/armnnOnnxParser/test/ProtoxtFixture.cpp
+            src/armnnOnnxParser/test/Relu.cpp
+            src/armnnOnnxParser/test/Reshape.cpp
             )
     endif()