Improve large-scale multitile destriping

[thomaswilliamsastro]

Keeping as draft for now, until I've checked it works across the Cy1 stuff

This PR addresses the persistent large-scale ripples in the data present across multiple tiles. It does a large-scale smooth and subtracts to try and fix any remaining stripes after the image stack has been produced. Previously this was after reprojection to the single tile, which caused edge-effects and rippled through to the background matching. It seems much more stable now, and the number of variables has decreased considerably

[thomaswilliamsastro]

off/on for NGC1300/F200W