Give self-attention raw, unprojected satellite imagery

[JackKelly]

One of the really cool things about using self-attention is that input images no longer have to confirm to a regular grid. Transformers view their inputs as a set.

So we don't have to project the satellite imagery. Instead we can give the attention mechanism the raw satellite data, but with OSGB coordinates. And the net will still be able to align with OSGB data like NWPs.

This might be nice because re-projection inevitably introduces artefacts.

But, one down-side is that we won't be able to redistribute the "raw" EUMETSAT data (their license forbids redistribution of "original numerical data"; but allows redistribution of transformed data)

#35