IVGCVSW-4439: Adding Elu support to Activation

 * Added CpuRef implementation
 * Added Unit Tests
 * Added Quantizer Test
 * Enabled Tests for Neon and CL backends on fp32 only
 * Added to Serializer

Signed-off-by: David Monahan <david.monahan@arm.com>
Change-Id: Ic23e1797dbc9352b40678c389d7fe2b836b582ea
diff --git a/include/armnn/Types.hpp b/include/armnn/Types.hpp
index af331a2..b00a8bf 100644
--- a/include/armnn/Types.hpp
+++ b/include/armnn/Types.hpp
@@ -62,7 +62,8 @@
     LeakyReLu   = 6,
     Abs         = 7,
     Sqrt        = 8,
-    Square      = 9
+    Square      = 9,
+    Elu         = 10
 };
 
 enum class ArgMinMaxFunction