IVGCVSW-4210 Create a public API for the common backend files

 * Create a public API for the common backend files
 * Move OutputHandler to armnn internal
 * Remove unused headers

Signed-off-by: Matteo Martincigh <matteo.martincigh@arm.com>
Signed-off-by: Narumol Prangnawarat <narumol.prangnawarat@arm.com>
Change-Id: I3e86d908b021e3561befa9d45158d87d2cbb18c0
diff --git a/Android.mk b/Android.mk
index 5439ef3..a8f96f5 100644
--- a/Android.mk
+++ b/Android.mk
@@ -95,6 +95,7 @@
         src/armnn/Observable.cpp \
         src/armnn/Optimizer.cpp \
         src/armnn/optimizations/PermuteAndBatchToSpaceAsDepthToSpace.cpp \
+        src/armnn/OutputHandler.cpp \
         src/armnn/ProfilingEvent.cpp \
         src/armnn/Profiling.cpp \
         src/armnn/Runtime.cpp \