IVGCVSW-2915 Add Merge Layer and no-op factory method

Change-Id: I54549671e0d3b207904cf9796a843eb2b0a631f7
Signed-off-by: Nattapat Chaimanowong <nattapat.chaimanowong@arm.com>
diff --git a/src/armnn/Network.cpp b/src/armnn/Network.cpp
index 6dbd461..73db2e8 100644
--- a/src/armnn/Network.cpp
+++ b/src/armnn/Network.cpp
@@ -966,6 +966,11 @@
     return m_Graph->AddLayer<GatherLayer>(name);
 }
 
+IConnectableLayer* Network::AddMergeLayer(const char* name)
+{
+    return m_Graph->AddLayer<MergeLayer>(name);
+}
+
 void Network::Accept(ILayerVisitor& visitor) const
 {
     for (auto layer : GetGraph())