Update requirements - Githubissues

Update lib_tflite_micro and lib_nn versions
Added support for x86 compile of vnr inference engine.
Modified vnr tests (all except the one using CFFI) to run for x86 target as well.
Added a convert script to convert from an input tflite model to everything needed to integrate it into the VNR module.
Added simple applications that I'm using now to analyse memory requirements for the VNR.

There are more changes coming but best to get this in as it's big enough already

xmos / fwk_voice