Impelement use of accelerate computations

Replace most repa computations with accelerate computations in performance critical functions, for now known to be "ConvolveOutP"

```
COST CENTRE                          MODULE    %time %alloc

convolveOutP.stencil.integrate       Main       70.3   69.8
convolveOutP.stencil.integrate.here  Main        8.5   11.3
convolveOutP.stencil.get'            Main        6.1    3.8
convolveOutP.stencil.integrate.(...) Main        5.3    0.0
convolveOutP                         Main        3.9    5.4
convolveOutP.stencil                 Main        1.6    0.0
conv2D                               Main        0.5    3.0
cnvLyr1.actvtn                       Main        0.3    1.0
convolve.tnsr4DDataFlt               Main        0.2    1.0
```