Adding CTest script

Adding script to run CTest on the Corstone-300 FVP. The script will
detect which version of the FVP that is used and pass the correct
command line arguments.

Updating README with instructions how to run tests, either using
CTest or calling the FVP directly.

Update FreeRTOS example to exit with the status of the inference.
Minor adjustments are needed to the output vectors.

Change-Id: I8a1a740b0dec2ce35d95e5c5d91f4b57a2c8e1fa