Fix armnn_external_delegate option parsing

 * Fixed the mechanism in armnn_delegate.cpp which creates the runtime
   options by moving it to DelegateOptions. BackendOptions are used in
   the runtime options as well as in the optimizer options but need
   to be processed separately.
 * Added runtime options to DelegateOptions to make it easier to differ
   between backend options of the runtime and the optimization
 * Updated armnn_external_delegate to use runtime options
 * Added explanations to OptimizerOptions

Signed-off-by: Jan Eilers <jan.eilers@arm.com>
Change-Id: I34235474147def261821e4576dd41a83ad492258
diff --git a/include/armnn/Types.hpp b/include/armnn/Types.hpp
index deaa0b3..f61a1fd 100644
--- a/include/armnn/Types.hpp
+++ b/include/armnn/Types.hpp
@@ -201,7 +201,7 @@
 /// The ShapeInferenceMethod modify how the output shapes are treated.
 /// When ValidateOnly is selected, the output shapes are inferred from the input parameters of the layer
 /// and any mismatch is reported.
-/// When InferAndValidate is selected 2 actions must be performed: (1)infer output shape from inputs and (2)validate the
+/// When InferAndValidate is selected 2 actions are performed: (1)infer output shape from inputs and (2)validate the
 /// shapes as in ValidateOnly. This option has been added to work with tensors which rank or dimension sizes are not
 /// specified explicitly, however this information can be calculated from the inputs.
 ///