IVGCVSW-1952 : add BackendId class to prepare for the replacement of Compute enum

!armnn:152674

Change-Id: I1bcdfdfbfb73e502d58f35717e2558e24651013c
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 501da80..dfda4d1 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -147,18 +147,23 @@
 
 list(APPEND armnn_sources
     include/armnn/ArmNN.hpp
+    include/armnn/BackendId.hpp
     include/armnn/Descriptors.hpp
     include/armnn/DescriptorsFwd.hpp
-    include/armnn/IRuntime.hpp
+    include/armnn/Exceptions.hpp
     include/armnn/ILayerSupport.hpp
     include/armnn/INetwork.hpp
+    include/armnn/IProfiler.hpp
+    include/armnn/IRuntime.hpp
+    include/armnn/LayerSupport.hpp
+    include/armnn/LstmParams.hpp
+    include/armnn/NetworkFwd.hpp
     include/armnn/Optional.hpp
     include/armnn/Tensor.hpp
     include/armnn/TensorFwd.hpp
     include/armnn/Types.hpp
     include/armnn/TypesUtils.hpp
     include/armnn/Utils.hpp
-    include/armnn/LayerSupport.hpp
     include/armnn/Version.hpp
     src/armnn/layers/LayerCloneBase.hpp
     src/armnn/layers/LayerWithParameters.hpp
@@ -378,6 +383,7 @@
         src/armnn/test/InstrumentTests.cpp
         src/armnn/test/ObservableTest.cpp
         src/armnn/test/OptionalTest.cpp
+        src/backends/test/BackendIdTests.cpp
         src/backends/test/BackendRegistryTests.cpp
         src/backends/test/IsLayerSupportedTestImpl.hpp
         src/backends/test/WorkloadDataValidation.cpp